Report - QSE GmbH€¦ · Consignment of samples was on 02 May, 2016. Participants analyzed the...

9th proficiency test for inhibitors May 2016

Report

QSE GmbH Steingruber Straße 6

91746 Weidenbach/Triesdorf Germany

Dipl.-Ing. (FH) Susanne Weidhaußer

Nadine Wolfsgruber Tel.: +49 (0)9826 / 62341

E-Mail: [email protected] [email protected]

of 20

Table of contents

1 Aim of proficiency test .......................................................................................................3

2 Performance of proficiency test .........................................................................................3

3 Production and inspection of test samples .........................................................................3

4 Participants .......................................................................................................................4

5 Results and evaluation .......................................................................................................4

5.1 Test systems ................................................................................................................... 4

5.2 Representation of the individual results ........................................................................ 5

5.3 Evaluation of the individual results .............................................................................. 14

5.4 Appraisal of the individual results ................................................................................ 16

5.5 Recommendations ........................................................................................................ 17

5.6 Comparison of the results of proficiency test for inhibitors 2008 to 2016 .................. 18

6 Summary ......................................................................................................................... 19

of 20

1 Aim of proficiency test

As an instrument of external quality assurance, proficiency tests offer laboratories the opportunity to monitor objectively their own performance in comparison to other laboratories.

Aim of this proficiency test for inhibitors was the detection of inhibitors or residues of veterinary medicinal products at MRL-level (maximum residue limits according to Regulation (EU) No 37/2010) by routine inhibitor testing of the participating laboratory.

2 Performance of proficiency test

Production and consignment of test samples were accomplished by AiM GmbH. Organization and evaluation of the proficiency test was carried out independently by QSE GmbH.

AiM GmbH Kaiser-Ludwig-Platz 2 D-80996 München

QSE GmbH Hochstatt 2 D-85283 Wolnzach

One test set consisted of 15 coded lyophilized UHT-milk samples. A defined volume of deionized sterile water for resuspending the samples and a detailed instruction for sample preparation were enclosed in each test set.

Each test set contained 8 samples with different inhibitor substances in concentration at MRL-level. The chosen substances Penicillin G, Cloxacillin, Ampicillin and Cefapirin are often used for treatment of lactating cows. The remaining 7 samples of the test set were inhibitor-free milk samples (table 1).

Table 1: Test set composition

Number of samples Inhibitor Concentration [µg/kg]

2 Penicillin G 4

2 Cloxacillin 30

2 Ampicillin 4

2 Cefapirin 60

7 - -

Consignment of samples was on 02 May, 2016. Participants analyzed the test samples with their test system, entered the results (positive/negative) in the evaluation sheet and sent the evaluation sheet to QSE GmbH by 20 May, 2016.

All participants received a certificate which affirmed their participation in the proficiency test. In case participants detected an added inhibitor-substance (Penicillin G, Cloxacillin, Ampicillin or Cefapirin) in concentration at MRL-level or the inhibitor-free samples correctly and therefore fulfilled the requirements of the present proficiency test, this was also stated in the certificate.

3 Production and inspection of test samples

To guarantee a varying order of substances (Penicillin G, Cloxacillin, Ampicillin, Cefapirin and inhibitor-free milk) in each test set, the test sets were randomized by a capable software. Afterwards it was ensured that all test sets varied regarding the spreading of substances as well as the spreading of positive and negative substances. Mistakes in sample labelling were avoided by producing and labelling the different substances separately and combining them into one test set afterwards.

of 20

To verify the concentrations of Penicillin G, Cloxacillin, Ampicillin and Cefapirin in the test samples, 2 bottles per substance were taken randomly from the whole batch. Prior to the proficiency test the samples were analyzed by an independent laboratory, accredited according to DIN EN ISO/IEC 17025:2005, with LC-MS/MS. The concentrations were affirmed1.

4 Participants

148 laboratories and organizations working in the dairy sector from altogether 19 countries participated in the proficiency test (figure 1).

Figure 1: Provenance of proficiency test participants

5 Results and evaluation

Altogether 168 test sets were forwarded to ring test participants. Feedback was submitted for 167 test sets. As some companies participated with several laboratories, test systems etc., altogether 357 test series were available for evaluation (table 2).

5.1 Test systems

In 169 test series inhibitor-analysis was performed with a microbiological inhibitor test and in 129 test series a rapid test was used. In 59 test series the used test system was not specified.

Numerous different test systems were applied. The most frequently used microbiological test systems were BRT Inhibitor Test (AiM GmbH), Delvotest BR (DSM) and Delvotest SP (DSM). With rapid tests BetaStar (Neogen), Charm-Test (Charm Sciences, Inc.) and Snap-Test (Idexx GmbH) dominated. The information on the test systems was given voluntarily by the participants.

1 We will be pleased to send you the laboratory report on request.

of 20

5.2 Representation of the individual results

The individual results of participants are shown in table 2. Samples in which an inhibitor was detected are marked with „+“, those in which no inhibitor was found were marked with „-". Empty fields mean that no feedback was received. Congenerous substances were numbered consecutively. The numeration corresponds in ascending order to the order of the substance in the test set.

Table 2: Individual results of participants

Test-series

Test system

Cloxacillin 30 µg/kg

Ampicillin 4 µg/kg

Penicillin G 4 µg/kg

Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

1 rapid test + + + + + + + + - - - - - - - 2 A rapid test + + + + + + + + - - - - - - - 2 B microbiological test - - + + + + + + - - - - - - - 3 A not specified + + + + + + + + - - - - - - - 3 B rapid test + + + + + + + + - - - - - - - 4 A microbiological test + + + + + + + + - - - - - - - 4 B rapid test + + + + + + + + - - - - - - - 5 not specified + + + + + + + + - - - - - - -

6 A microbiological test + + + + + + + + - - - - - - - 6 B rapid test + + + + + + + + - - - - - - - 6 C microbiological test + + + + + + + + - - - - - - - 6 D rapid test + + + + + + + + - - - - - - - 7 microbiological test + + + + + + + + - - - - - - -

8 A microbiological test - - + + + + + + - - - - - - - 8 B microbiological test - - + + + + + + - - - - - - - 8 C microbiological test - - + + + + + + - - - - - - - 9 A not specified + + + + + + + + - - - - - - - 9 B not specified + + + + + + + + - - - - - - -

10 A not specified + + + + + + + + - - - - - - - 10 B rapid test + + + + + + + + - - - - - - - 11 A microbiological test + + + + + + + + - - - - - - - 11 B rapid test + + + + + + + + - - - - - - - 12 A microbiological test + + + + + + + + - - - - - - -

12 AA microbiological test + + + + + + + + - - - - - - - 12 B rapid test + + + + + + + + - - - - - - -

12 BB rapid test + + + + + + + + - - - - - - - 13 microbiological test + + + + + + + + - - - - - - -

14 A microbiological test + + + + + + + + - - - - - - - 14 B microbiological test + + + + + + + + - - - - - - - 15 A rapid test + + + + + + + + - - - - - - - 15 B microbiological test + + + + + + + + - - - - - - - 15 C microbiological test + + + + + + + + - - - - - - - 16 A microbiological test + + + + + + + + - - - - - - - 16 B rapid test + + + + + + + + - - - - - - - 17 microbiological test + + + + + + + + - - - - - - -

of 20

Table 2: Individual results of participants (continued)

Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

18 A microbiological test + + + + + + + + - - - - - - - 18 B rapid test + + + + + + + + - - - - - - - 18 C microbiological test + + + + + + + + - - - - - - - 18 D rapid test + + + + + + + + - - - - - - - 19 not specified + + + + + + + + - - - - - - - 20 not specified + + + + + + + + - - - - - - -

21 A rapid test + + + + + + + + - - - - - - - 21 B rapid test + + + + + + + + - - - - - - - 22 rapid test - - - - + + + + - - - - - - - 23 rapid test + + + + + + + + - - - - - - -

24 A microbiological test + + + + + + + + - - - - - - - 24 B rapid test + + + + + + + + - - - - - - - 25 A microbiological test + + + + + + + + - - - - - - - 25 B rapid test + + + + + + + + - - - - - - - 26 A not specified + + + + + + + + - - - - - - - 26 B not specified + + + + + + + + - - - - - - - 27 A microbiological test + + + + + + + + - - - - - - - 27 B rapid test - - + + + + + + - - - - - - - 28 A microbiological test + + + + + + + + - - - - - - - 28 B rapid test - - + + + + + + - - - - - - - 29 microbiological test + + + + + + + + - - - - - - - 30 rapid test + + + + + + + + - - - - - - -

31 A rapid test + + + + + + + + - - - - - - - 31 B microbiological test + + + + + + + + - - - - - - - 31 C rapid test + + + + + + + + - - - - - - - 32 microbiological test + + + + + + + + - - - - - - -

33 A not specified + + + + + + + + - - - - - - - 33 B not specified + + - - + + + + - - - - - - - 34 A not specified - - + + + + + + - - - - - - - 34 B not specified + + + - + + + + - - - - - - - 35 A microbiological test + + + + + + + + - - - - - - - 35 B microbiological test + + + + + + + + - - - - - - - 35 C microbiological test + + + + + + + + - - - - - - - 36 A microbiological test + + + + + + + + - - - - - - - 36 B rapid test + + + + + + + + - - - - - - - 37 microbiological test - - + + + + + + - - - - - - - 38 microbiological test + + + + + + + + - - - - - - - 39 microbiological test + + + + + + + + - - - - - - - 40 not specified + + + + + + + + - - - - - - -

41 A not specified + + + + + + + + - - - - - - - 41 B rapid test + + - + + + + + - - - - - - - 42 microbiological test + + + + + + + + - - - - - - -

of 20


Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

43 A not specified - - + + + + + + - - - - - - - 43 B not specified - - + + + + + + - - - - - - - 43 C not specified - - + + + + + + - - - - - - - 44 not specified + + + + + + + + - - - - - - -

45 A microbiological test + + + + + + + + - - - - - - - 45 B rapid test + + + + + + + + - - - - - - - 46 A microbiological test + + + + + + + + - - - - - - - 46 B rapid test + + + + + + + + - - - - - - - 47 microbiological test + + + + + + + + - - - - - - - 48 microbiological test + + + + + + + + - - - - - - -

49 A rapid test - - + + + + + + - - - - - - - 49 B microbiological test + + + + + + + + - - - - - - - 49 C rapid test + + + + + + + + - - - - - - - 50 A microbiological test - - + + + + + + - - - - - - - 50 B microbiological test + + + + + + + + - - - - - - - 50 C rapid test + + + + + + + + - - - - - - - 51 microbiological test + + + + + + + + - - - - - - - 52 microbiological test + + + + + + + + - - - - - - -

53 A not specified - - + + + + + + - - - - - - - 53 B rapid test + + + + + + + + - - - - - - - 54 A microbiological test + + + + + + + + - - - - - - - 54 B rapid test + + - + + + + + - - - - - - - 55 microbiological test + + + + + + + + - - - - - - -

56 A microbiological test + + + + + + + + - - - - - - - 56 B rapid test - - + + + + + + - - - - - - - 57 A microbiological test - - + + + + + + - - - - - - - 57 B rapid test - - + + + + + + - - - - - - - 58 A microbiological test + + + + + + + + - - - - - - - 58 B microbiological test - - + + + + + + - - - - - - - 58 C microbiological test - - + + + + + + - - - - - - - 58 D rapid test + + + + + + + + - - - - - - - 58 E rapid test + + + + + + + + - - - - - - - 59 A microbiological test + + + + + + + + - - - - - - - 59 B microbiological test + + + + + + + + - - - - - - - 59 C microbiological test + + + + + + + + - - - - - - - 59 D rapid test + + + + + + + + - - - - - - - 60 A microbiological test + + + + + + + + - - - - - - - 60 B microbiological test + + + + + + + + - - - - - - - 60 C microbiological test + + + + + + + + - - - - - - - 60 D rapid test + + + - + + + + - - - - - - - 61 microbiological test - - - + + + + + - - - - - - -

62 A microbiological test + + + + + + + + - - - - - - -

of 20


Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

62 AA rapid test + - + + + + + + - - - - - - - 62 B microbiological test + + + + + + + + - - - - - - -

62 BB rapid test + - + + + + + + - - - - - - - 63 microbiological test + + + + + + + + - - - - - - -

64 A microbiological test + + + + + + + + - - - - - - - 64 B not specified + + + + + + + + - - - - - - - 64 C rapid test + + + + + + + + - - - - - - - 65 A rapid test - - + + + + + + - - - - - - - 65 B microbiological test + + + + + + + + - - - - - - - 65 C microbiological test + + + + + + + + - - - - - - - 65 D rapid test - - + + + + + + - - - - - - - 66 microbiological test + + + + + + + + - - - - - - -

67 A microbiological test + + + + + + + + - - - - - - - 67 B rapid test + + + + + + + + - - - - - - - 67 C rapid test + + + + + + + + - - - - - - - 68 A microbiological test + + + + + + + + - - - - - - - 68 B rapid test + + + + + + + + - - - - - - - 69 A microbiological test + + + + + + + + - - - - - - - 69 B rapid test + - + + + + + + - - - - - - - 70 not specified + + + + + + + + - - - - - - - 71 microbiological test + + + + + + + + - - - - + + - 72 rapid test + + + + + + + + - - - - - - -

73 A microbiological test + + + + + + + + - - - - - - - 73 B rapid test + + - + + + + + - - - - - - - 73 C rapid test + + + + + + + + - - - - - - - 74 microbiological test + + + + + + + + - - - - - - - 75 rapid test + + + + + + + + - - - - - - -

76 A rapid test + + + + + + + + - - - - - - - 76 B microbiological test + + + + + + + + - - - - - - - 77 A microbiological test - - + + + + + + - - - - - - - 77 B microbiological test + + + + + + + + - - - - - - - 77 C rapid test - - + + + + + + - - - - - - - 78 microbiological test + + + + + + + + - - - - - - -

79 A rapid test + + + + + + + + - - - - - - - 79 B microbiological test + + + + + + + + - - - - - - -

79 C microbiological test - - + + + + + + - - - - - - - 80 A not specified + + + + + + + + - - - - - - - 80 B not specified + + + + + + + + - - - - - - - 81 not specified + + + + + + + + - - - - - - - 82 rapid test + + + + + + + + - - - - - - -

83 A microbiological test + + + + + + + + - - - - - - - 83 B rapid test + + + + + + + + - - - - - - -

of 20


Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

84 no feedback 85 A not specified + + + + + + + + - - - - - - - 85 B not specified + + + + + + + + - - - - - - - 86 not specified + + + + + + + + - - - - - - -

87 A not specified + + + + + + + + - - - - - - - 87 B not specified + + + + + + + + - - - - - - - 88 A microbiological test + + + + + + + + - - - - - - - 88 B rapid test + + + + + + + + - - - - - - - 88 C rapid test + + + + + + + + - - - - - - - 89 A microbiological test + + + + + + + + - - - - - - - 89 B rapid test + + + + + + + + - - - - - - - 89 C microbiological test + + + + + + + + - - - - - - - 90 A not specified + + + + + + + + - - - - - - - 90 B not specified - - + + + + + + - - - - - - - 91 A microbiological test + + + + + + + + - - - - - - - 91 B microbiological test + + + + + + + + - - - - - - - 91 C microbiological test - - + + + + + + - - - - - - - 92 A microbiological test + + + + + + + + - - - - - - - 92 B rapid test + + + + + + + + - - - - - - - 92 C microbiological test - - + + + + + + - - - - - - - 92 D microbiological test + + + + + + + + - - - - - - - 92 E rapid test + + + + + + + + - - - - - - - 92 F microbiological test - - + + + + + + - - - - - - - 92 G microbiological test + + + + + + + + - - - - - - - 92 H rapid test + + + + + + + + - - - - - - - 92 I microbiological test - - + + + + + + - - - - - - - 93 A microbiological test + + + + + + + + - - - - - - - 93 B rapid test + + + + + + + + - - - - - - - 93 C microbiological test - - + + + + + + - - - - - - - 93 D microbiological test + + + + + + + + - - - - - - - 93 E rapid test + + + + + + + + - - - - - - - 93 F microbiological test - - + + + + + + - - - - - - - 93 G microbiological test + + + + + + + + - - - - - - - 93 H rapid test + + + + + + + + - - - - - - - 93 I microbiological test - - + + + + + + - - - - - - - 94 A not specified + + + + + + + + - - - - - - - 94 B not specified + + + + + + + + - - - - - - - 94 C not specified + + + + + + + + - - - - - - - 95 A microbiological test + + + + + + + + - - - - - - -

95 AA rapid test + + + + + + + + - - - - - - - 95 B microbiological test + + + + + + + + - - - - - - -

95 BB rapid test + + - - + + + + - - - - - - -

of 20


Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

96 microbiological test + + + + + + + + - - - - - - - 97 A microbiological test + + + + + + + + - - - - - - - 97 B rapid test + + + + + + + + - - - - - - - 98 A microbiological test + + + + + + + + - - - - - - - 98 B rapid test + + + + + + + + - - - - - - - 99 A microbiological test + + + + + + + + - - - - - - - 99 B rapid test - - + + + + + + - - - - - - - 100 microbiological test + + + + + + + + - - - - - - -

101 A not specified + + + + + + + + - - - - - - - 101 B not specified + + + + + + + + - - - - - - - 102 A microbiological test + + + + + + + + - - - - - - - 102 B microbiological test + + + + + + + + - - - - - - - 102 C microbiological test + + + + + + + + - - - - - - - 102 D rapid test + + + + + + + + - - - - - - - 102 E rapid test + + + - + + + + - - - - - - - 103 A microbiological test + + + + + + + + - - - - - - - 103 B microbiological test + + + + + + + + - - - - - - - 103 C rapid test - - + + + + + + - - - - - - - 104 A microbiological test + + + + + + + + - - - - - - - 104 B microbiological test + + + + + + + + - - - - - - - 104 C rapid test - - + + + + + + - - - - - - - 105 A microbiological test + + + + + + + + - - - - - - - 105 B rapid test - - + + + + + + - - - - - - - 106 A microbiological test + + + + + + + + - - - - - - - 106 B microbiological test + + + + + + + + - - - - - - - 106 C rapid test - - + + + + + + - - - - - - - 107 A microbiological test + + + + + + + + - - - - - - - 107 B microbiological test + + + + + + + + - - - - - - - 107 C microbiological test + + + + + + + + - - - - - - - 107 D rapid test + + - + + + + + - - - - - - - 107 E rapid test - + + + + + + + - - - - - - - 108 A microbiological test + + + + + + + + - - - - - - - 108 B rapid test + + + + + + + + - - - - - - - 109 microbiological test + + + + + + + + - - - - - - - 110 rapid test + + + + + + + + - - - - - - - 111 microbiological test + + + + + + + + - - - - - - -

112 A microbiological test + + + + + + + + - - - - - - - 112 B rapid test + + + + + + + + - - - - - - - 113 A microbiological test + + + + + + + + - - - - - - - 113 B rapid test + + + + + + + + - - - - - - - 113 C rapid test + + + + + + + + - - - - - - - 114 A rapid test + + + + + + + + - - - - - - -

of 20


Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

114 B microbiological test + + + + + + + + - - - - - - - 114 C microbiological test - - + + + + + + - - - - - - - 115 A microbiological test + + + + + + + + - - - - - - - 115 B microbiological test + + + + + + + + - - - - - - - 116 A microbiological test + + + + + + + + - - - - - - - 116 B rapid test + + + + + + + + - - - - - - - 117 A not specified + + + + + + + + - - - - - - - 117 B rapid test + + + + + + + + - - - - - - - 118 A microbiological test + + + + + + + + - - - - - - - 118 B microbiological test - - + + + + + + - - - - - - - 118 C rapid test + + + + + + + + - - - - - - - 119 microbiological test - - + + + + + + - - - - - - -

120 A not specified - - + + + + + + - - - - - - - 120 B rapid test + + + + + + + + - - - - - - - 121 A microbiological test + + + + + + + + - - - - - - - 121 B microbiological test + + + + + + + + - - - - - - - 121 C rapid test + + + + + + + + - - - - - - - 121 D microbiological test + + + + + + + + - - - - - - - 121 E microbiological test + + + + + + + + - - - - - - - 121 F microbiological test + + + + + + + + - - - - - - - 121 G microbiological test + + + + + + + + - - - - - - - 121 H microbiological test + + + + + + + + - - - - - - - 121 I microbiological test + + + + + + + + - - - - - - - 121 J microbiological test + + + + + + + + - - - - - - - 121 K microbiological test + + + + + + + + - - - - - - - 122 A rapid test + + + + + + + + - - - - - - - 122 B rapid test + + + + + + + + - - - - - - - 122 C rapid test + + + + + + + + - - - - - - - 122 D rapid test + + + + + + + + - - - - - - - 122 E rapid test + + + + + + + + - - - - - - - 122 F microbiological test + + + + + + + + - - - - - - - 122 G microbiological test + + + + + + + + - - - - - - - 122 H rapid test + + + + + + + + - - - - - - - 123 rapid test + + + + + + + + - - - - - - -

124 A microbiological test + + + + + + + + - - - - - - -

124 B rapid test + + + + + + + + - - - - - - - 125 microbiological test + + + + + + + + - - - - - - -

126 A not specified + + + + + + + + - - - - - - - 126 B not specified + + + + + + + + - - - - - - - 127 A not specified + + + + + + + + - - - - - - - 127 B rapid test + + + + + + + + - - - - - - - 128 rapid test + + + + + + + + - - - - - - -

of 20


Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

129 A rapid test + + + + + + + + - - - - - - - 129 B microbiological test + + + + + + + + - - - - - - - 130 A microbiological test + + + + + + + + - - - - - - - 130 B rapid test + + + + + + + + - - - - - - - 131 A not specified - - + + + + + + - - - - - - - 131 B not specified + + + - + + + + - - - - - - - 132 A microbiological test + + + + + + + + - - - - - - - 132 B rapid test + + - - + + + + - - - - - - - 133 A not specified - - + + + + + + - - - - - - - 133 B not specified + + - + + + + + - - - - - - - 134 A microbiological test + + + + + + + + - - - - - - - 134 B rapid test + + + - + + + + - - - - - - - 135 A rapid test + + + + + + + + - - - - - - - 135 B microbiological test - - + + + + + + - - - - - - - 136 A microbiological test - - + + + + + + - - - - - - - 136 B rapid test + + - - + + + + - - - - - - - 137 rapid test + + - + + + + + - - - - - - -

138 A microbiological test - - + + + + + + - - - - - - - 138 B rapid test + + - + + + + + - - - - - - - 139 A microbiological test + + + + + + + + - - - - - - - 139 B rapid test + + - - + + + + - - - - - - - 140 not specified + + + + + + + + - - - - - - -

141 A microbiological test + + + + + + + + - - - - - - - 141 B microbiological test + + + + + + + + - - - - - - - 141 C microbiological test + + + + + + + + - - - - - - - 141 D rapid test + + + + + + + + - - - - - - - 141 E rapid test + + + + + + + + - - - - - - - 141 F rapid test - - + + + + + + - - - - - - - 141 G rapid test - - + + + + + + - - - - - - - 141 H rapid test + + + + + + + + - - - - - - - 141 I rapid test + + + + + + + + - - - - - - - 142 microbiological test + + + + + + + + - - - - - - - 143 microbiological test + + + + + + + + - - - - - - -

144 A microbiological test + + + + + + + + - - - - - - - 144 B rapid test + + + + + + + + - - - - - - - 145 not specified + + + + + + + + - - - - - - -

146 A microbiological test + + + + + + + + - - - - - - - 146 B rapid test + + - - + + + + - - - - - - - 147 A not specified + + + + + + + + - - - - - - - 147 B not specified + + + + + + + + - - - - - - - 148 microbiological test + + + + + + + + - - - - - - -

149 A rapid test + + + + + + + + - - - - - - -

of 20


Test-series

Test system


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Inhibitor-free milk

1 2 1 2 1 2 1 2 1 2 3 4 5 6 7

150 B rapid test + + + + + + + + - - - - - - - 151 C microbiological test + + + + + + + + - - - - - - - 152 A microbiological test - - + + + + + + - - - - - - - 152 B rapid test + + + + + + + + - - - - - - - 152 C rapid test + + + + + + + + - - - - + - - 153 microbiological test + + + + + + + + - - - - - - -

154 A not specified + + + + + + + + - - - - - - - 154 B not specified - - + + + + + + - - - - - - - 154 C not specified + + + + + + + + - - - - - - - 154 D not specified + + + + + + + + - - - - - - - 155 microbiological test + + + + + + + + - - - - - - - 156 rapid test + + + + + + + + - - - - - - - 157 not specified + + + + + + + + - - - - - - -

158 A microbiological test - - + + + + + + - - - - - - - 158 B rapid test + + - - + + + + - - - - - - - 159 not specified - - + + + + + + - - - - - - - 160 microbiological test + + + + + + + + - - - - - - - 161 microbiological test + + + + + + + + - - - - - - -

162 A rapid test + + + + + + + + - - - - - - - 162 B not specified + + + + + + + + - - - - - - - 163 A microbiological test + + + + + + + + - - - - - - - 163 B rapid test + + + + + + + + - - - - - - - 164 A microbiological test + + + + + + + + - - - - - - - 164 B rapid test + + + + + + + + - - - - - - - 165 not specified - - - + + + + + - - - - - - - 166 not specified - - + + + + + + - - - - - - -

168 A microbiological test + + + + + + + + - - - - - - - 168 B rapid test + + + + + + + + - - - - - - - 168 C rapid test + + + + + + + + - - - - - - -

2 green framed samples: samples were near detection limit or result was ambiguous 3 blue hatched samples: participant had difficulties with solving the lyophilisate

of 20

5.3 Evaluation of the individual results

One participant had difficulties with solving the lyophilized samples. The detection of inhibitor substances was not negatively influenced (table 2).

Table 3: Representation of results in summary

Inhibitor-

free samples

Inhibitor- spiked

samples


Ampicillin 4 µg/kg


Cefapirin 60 µg/kg

Samples per test set 7 8 2 2 2 2

Forwarded samples 1176 1344 336 336 336 336

Confirmed samples 1169 1336 334 334 334 334

All Test Systems

Confirmed results 2499 2856 714 714 714 714

Number of negative results 2496 145 116 29 0 0

Number of positive results 3 2711 598 685 714 714

Negative results [%] 99,9 5,1 16,2 4,1 0,0 0,0

Positive results [%] 0,1 94,9 83,8 95,9 100,0 100,0

Microbiological Test Systems






Rapid Test Systems






Other Test Systems / Not specified Test Systems






of 20

Evaluation of the individual results showed, that inhibitor-free milk samples were identified 99,9 % as inhibitor-negative. Altogether 3 false-positive results were detected in 2 of 357 evaluated test series (table 2 and 3, figure 2).

The evaluation of all test systems (microbiological tests, rapid tests and other/not specified tests) showed, that Cloxacillin was detected 83,8 %, Ampicillin 95,9 %, Penicillin G 100,0 % and Cefapirin 100,0 % as inhibitor-positive. Altogether in the present proficiency test 94,9 % of the inhibitor-spiked samples were detected inhibitor-positive (table 3, figure 2).

Figure 2: Accuracy of individual results [%] for all test systems (microbiological tests, rapid tests and other/not specified tests)4

Figure 3: Accuracy of individual results [%] for all microbiological test systems4

With microbiological test systems 84,0 % of the samples spiked with Cloxacillin were stated as inhibitor-positive. With rapid tests 86,0 % and with other/not specified tests 78,0 % of the Cloxacillin-spiked samples were detected positive (table 3, figure 3 and 4).

With microbiological tests Ampicillin was identified 100,0 % as inhibitor-positive. With rapid tests 91,1 % and with other/not specified tests 94,9 % of the Ampicillin-spiked samples were detected inhibitor-positive (table 3, figure 3 and 4).

4 „False results“ include all inhibitor-spiked samples, which were detected inhibitor-negative and all inhibitor-free samples, which were detected inhibitor-positive. “Correct results” include all inhibitor-spiked samples, which were detected inhibitor-positive and all inhibitor-free samples, which were detected inhibitor-negative.

of 20

With microbiological tests Penicillin G-spiked samples were identified 100,0 % as inhibitor-positive. With rapid tests Penicillin G was detected inhibitor-positive in 100,0 % and with other/not specified tests in 100,0 % of the results (table 3, figure 3 and 4).

With microbiological test systems Cefapirin was detected inhibitor-positive in 100,0 %, with rapid tests in 100,0 % and with other/not specified tests in 100,0 % of the results (table 3, figure 3 and 4).

Figure 4: Accuracy of individual results [%] for all rapid test systems4

5.4 Appraisal of the individual results

The aim of proficiency tests is primarily the appraisal of the capability of the participating laboratories. An identification of potential sources of error can increase the quality of performance. In the present proficiency test therefore false results4 were observed with particular advertency.

Most participants gave voluntary information on the test system which was used. The appraisal of the test systems is not the aim of the present proficiency test, but due to the extensive information, the test systems could be included in the following appraisement.

Appraisal of the false-positive inhibitor-free samples

In 2 of 357 evaluated test series inhibitor-free milk was detected false-positive (table 2). A possible reason for false-positive results is a carry-over from inhibitor-spiked samples to inhibitor-free milk during test performance. If also inhibitor-spiked samples were detected not correctly (not in this case), a mix-up of inhibitor-free and inhibitor-spiked samples within the test set cannot be excluded. A mix-up during labelling of the samples can be excluded (chapter 3).

Appraisal of false-negative inhibitor-spiked samples

If inhibitor-spiked samples are detected false-negative this can have diverse reasons. On one hand mistakes in sample preparation or test performance, insufficient incubation or non-observance of the manufacturer’s instructions can have a negative influence on the result. On the other hand also the tolerance of the test systems and the reading devices must be considered. According to some participants, results were near the classification limit (table 2). How such doubtful results are classified in routine inhibitor testing is finally in the responsibility and objective of the laboratories.


of 20

The aim of the present proficiency test was the detection of inhibitor substances at MRL-level. The inhibitor-substances Ampicillin, Cloxacillin, Cefapirin and Penicillin G were added in appropriate concentrations (table 1) and were tested and affirmed by an independent institute (chapter 3). Noticeable was, that with microbiological test systems most time all substances of the same inhibitor-group were detected positive or negative homogeneously. With rapid test systems there were more often different results for the same substance.

In 21 of 357 evaluated test series Ampicillin-spiked samples were detected false-negative (table 2). Especially with rapid tests Ampicillin was not identified correctly.

Of the 357 evaluated test series no Penicillin G-spiked samples were stated false-negative (table 2).

Cloxacillin was detected false-negative in 60 of 357 evaluated test series (table 2). There was an obvious accumulation of false-negative Cloxacillin-results with one microbiological test system and one rapid test system.

Cefapirin was not detected false-negative in any of the test series (table 2).


5.5 Recommendations

Several reasons may cause negative results of samples containing inhibitors at MRL-level or false-positive results of inhibitor free samples. If mistakes as e. g. mix-up of the samples can be excluded, checking the sample preparation and testing execution is recommended. Therefore the procedures have to be checked step by step against the manufacturer’s instructions. Special attention should be paid to the volume, temperature and condition of the sample. Common sources of error are:

Sample preparation and storage

Mistakes in pipetting, carry-over effects and contaminated laboratory equipment

Mix-up, inappropriate storage and exceeding the expiry date of chemicals.

Inappropriate storage and exceeding the expiry date of test kits.

Use of test kits and chemicals batches not belonging together (rapid tests)

Incubation of test systems (temperature, time)

Operation and calibration of the reading device

Generally we strongly recommend using appropriate positive and negative controls for the inhibitor analysis and the calibration of the reading devices. On the one hand, the controls give users clear evidence that the system is functioning properly. On the other hand the controls help to evaluate the samples. Above all, the ideal end point of the incubation for the microbiological test systems is clearly determined by the complete decolouration of the negative control.

of 20

5.6 Comparison of the results of proficiency test for inhibitors 2008 to 2016

Figures 5 to 7 show the results of the present proficiency test for inhibitors in comparison to the results of the proficiency tests for inhibitors in the years 2008 to 2015. The inhibitor-substance Cefapirin was included in the ring test for the first time in 2011.

Figure 5: Comparison of the ring test results 2008 to 2016 for all test systems (microbiological tests, rapid tests and other/not specified tests Tests)

4

Figure 6: Comparison of the ring test results 2008 to 2016 for all microbiological test systems4


of 20

Figure 7: Comparison of the ring test results 2008 to 2016 for all rapid test systems4

In 2016 the results of the previous years for the substances Penicillin G, Cefapirin and the inhibitor-free milk were mostly confirmed. The detection of Penicillin G, Cefapirin and the inhibitor-free milk samples is quite assured. With microbiological Test Systems and with Rapid Test Systems Cloxacillin was detected with a lower security compared to the last year. Likewise with Rapid Test Systems Ampicillin was detected with a higher security compared to the last year. Detection of Cloxacillin and also the detection of Ampicillin is only of limited reliability (figure 5 to 7).


6 Summary

Production and consignment of test samples were accomplished by AiM GmbH. Organization and evaluation of proficiency test were carried out independently by QSE GmbH.

One test set consisted of 15 lyophilized UHT-milk samples. Each test set contained the inhibitor substances Cloxacillin (2 samples), Ampicillin (2 samples), Penicillin G (2 samples) and Cefapirin (2 samples), each in the concentration of the MRL. The remaining 7 samples of the test set were inhibitor-free milk samples.

148 laboratories and organizations working in the dairy sector from 19 nations participated in the proficiency test. Altogether 357 test series contributed to the evaluation, whereas in 169 test series a microbiological inhibitor test and in 129 test series a rapid test was used. In 59 test series the test system was not specified.

Evaluation of the individual results showed, that inhibitor-free milk samples were identified 99,9 % as inhibitor-negative. In 2 of 357 evaluated test series inhibitor-free milk was detected false-positive.

of 20

In the proficiency test, which represents the routine inhibitor analysis, 5,1 % of the inhibitor-spiked samples were identified as inhibitor-negative.

o 16,2 % of samples which were spiked with Cloxacillin, were not detected as inhibitor-positive.

o 4,1 % of samples which were spiked with Ampicillin, were not detected as inhibitor-positive.

o 0,0 % of samples which were spiked with Penicillin G, were not detected as inhibitor-positive.

o 0,0 % of samples which were spiked with Cefapirin, were not detected as inhibitor-positive.

With microbiological tests Cefapirin was detected 100,0 %, Penicillin G 100,0 %, Ampicillin 100,0 % and Cloxacillin 84,0 % as inhibitor-positive. With rapid tests Cefapirin was identified 100,0 %, Penicillin G 100,0 %, Cloxacillin 86,0 % and Ampicillin 91,1 % as inhibitor-positive.

Generally it can be assumed that the detection of Cefapirin and Penicillin G in concentration of MRL in routine analysis is quite assured. Compared to the last years, the detection of Ampicillin improved whereas the detection of Cloxacillin deteriorated. The detection reliability of Ampicillin and Cloxacillin still is limited.

In chapter 5.5 recommendations are listed how to identify reasons for false results4. If the reasons cannot be identified in-house, the organizer of the proficiency test is pleased to support the participants individually.


Report - QSE GmbH€¦ · Consignment of samples was on 02 May, 2016. Participants analyzed the...

Documents

Transcript of Report - QSE GmbH€¦ · Consignment of samples was on 02 May, 2016. Participants analyzed the...