UNRULY CATS – NAUGHTY BUT - blood · antibody titres of pregnant patients referred for ... of the...
Transcript of UNRULY CATS – NAUGHTY BUT - blood · antibody titres of pregnant patients referred for ... of the...
Background
• Discrepancies were noted at our institution in antibody titres of pregnant patients referred for specialist management of HDFN.
• To investigate the cause of these differences an audit of current Australian practice was proposed.
• A survey was conducted to determine details of existing titre methods and to see how present practice has drifted from the recommendations of the ANZSBT for the NICE tube titration method developed in 1996.
Monitoring antibody levels of alloimmunized women (with potentially clinically significant antibodies) during pregnancy in Australia.
• Location • Range of antibodies • Titration techniques • Use of ANZSBT guidelines• Endpoint scores• Clinical significance
Questionnaire:
• Diluents• Pooled cells• Frequency of testing• Numbers• Quantitation
Number of samples tested
0
1
2
3
4
5
6
<1 1 2 3 4 5 6 7 8 9 10 12 16 20 25 50 100 160 180
Number of samples / month
Labo
rato
ries
Surv
eyed
Range of antibodies
All laboratories performed titrations on antibodies other than Rh
• 17% titred Group 1 (ANZSBT – Rh, Kell and Fya)• 60% titred Group 1 + 2 antibodies (Fyb, Kidd, Ss, M)• 23% no details given
ANZSBT Guidelines 3rd Ed 2007
Appendix 1 ‐ Titration Method1. Prepare master dilutions of the serum/plasma using a minimum volume of 250μL and a diluent of 5% protein in Buffered Saline (pH 7.0 ‐ 7.2).2. Prepare a 3% washed cell suspension in Buffered Saline (pH 7.0 ‐7.2). These cells should be a pool of equal volumes of cells homozygous for the antigen being tested3. Transfer 200μL of serum/plasma or serum/plasma dilution into a tube. Add 50uL of the cell suspension.4. Mix and incubate at 37C for 30 minutes.5. Wash 3 times in PBS and add AHG, mix, spin and read.6. The end point is read as the last tube showing a score 5 (1+) reaction.Developed by a NICE (National Immunohaematology Continuing Education) consensus forum.
Diluents
Tube
3% Albumin4% Albumin5% Albumin6% AlbuminSaline
CAT
3% Albumin3-4% Albumin5% Albumin6% AlbuminSaline
Frequency of titration
• 74% of labs surveyed provided advice on the frequency of testing during pregnancy
• 64% quoted ANZSBT guidelines• 26% left this decision to the clinician
Clinical significance (Anti‐D)
0
5
10
15
20
25
>4 >16 >32 Leftinterpretationto clinicians
Did notunderstand
the question
Quantitation of anti‐D and anti‐c
Victoria was the only state that did not monitor by quantitation (with one pathology service being the exception)
All other states sent samples for quantitation(except for two laboratories surveyed)
Testing was done by ARCBS Perth, ARCBS Sydney and South Australian Women’s and Children’s Hospital
References1. ANZSBT Guidelines for blood grouping and antibody screening in the
antenatal and perinatal setting [3rd Ed updated March 2007; cited 2011 Nov 24]. Available from: http://www.anzsbt.org.au/publications/#societyg
2. Putrino A, Allwright J, Wheeler M. Comparison of antenatal antibody titres by automated analyser and manual tube technique [poster presentation]. Monash Medical Centre, Melbourne; 2008.
3. Aitken G, Bates G, Triffitt D, et al. Tasmanian state‐wide study [poster presentation]. Tasmania; 2006.
4. Shin SY, Kwon KC, Koo SH, et al. Evaluation of two automated instruments for pre‐transfusion testing: Auto Vue Innova and Techno TwinStation. Korean J Lab Med. 2008;28:214‐20.
5. Aubuchon JP, de Wildt‐Eggen J, Dumont LJ. Reducing the variation in performance of antibody titrations. Arch Pathol lab Med. 2008;132:1194‐1201.
6. Novaretti MCZ, Jens E, Pagliarini T, et al. Comparison of conventional tube test with Diamed gel micro‐column assay for anti‐D titration. Clin Lab Haem. 2003;25:311‐15.