Medical Devices and LAL Testing
Transcript of Medical Devices and LAL Testing
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Medical Devices
and LAL Testing
Associates of Cape Cod, Inc.
Laurie Fife
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Associates of Cape Cod, Inc.
� Falmouth, Massachusetts
� FDA Licensed Manufacturer, License #700, ISO 13485 Certified
� 80,000 square foot state-of-the-art manufacturing building including:
Class 100,000, Class 10,000 and Class 100 workspace
Research and Development
Contract Testing Services
Customer Service
Technical Service
Corporate Offices
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1974 1993 20021985 1997
ACC History
1977
Company
founded by
Dr. Stanley
Watson
ACC is first company
Licensed by FDA for LAL
ACC introduces first
LAL instrumentation
1995
First FDA License for
all 3 LAL assays
ACC establishes
offices in the UK
and Germany
Seikagaku purchases
ACC, merges with
Seikagaku America
New 80,000sq ft facility
completed in Falmouth
Technology Park
Contract Testing
Services
established
2004
Fungitell™ approved
by FDA for IFI detection
Beacon™
Diagnostic
Lab
established
1979 2003
Pyrosoft-11
Launched, 21 CFR
P11 compliant
software
NorthStar
Bioproducts
established
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Limulus Amebocyte Lysate
• LAL
• An extract that forms a clot in the presence of endotoxin
+
nucleolus granules
pseudopodia
+
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1 billion gram negative bacteria/mL (seawater sample stained with AcridineOrange)
Ocean Environment
vibrio
bacillus
spirillumcocci
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Host Defense Mechanism
• Granules contain clotting factor/ enzymes
• The crab can survive having most of its blood clot
nucleus,
nucleolus
granules
pseudopodia
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Host Defense Mechanism
• Gram-negative bacteria or endotoxin causes blood cells (amebocytes) to release proteins into the plasma (hemolymph) causing the blood to coagulate
• Coagulation kills bacteria and neutralizes endotoxin
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History and Discovery of LAL
• The earliest work on horseshoe crab blood was carried out in the late 1800’s
• Bang described a bacterial disease of the horseshoe crab (1953)
• Levin and Bang demonstrated clotting with endotoxin in vitro (1960’s)
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Levin and Bang’s Impact
• Strong clinical interest
• Mixed Clinical results
• Pharmaceutical companies becameinterested
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LAL and USP Pyrogen Test
• Mascoli and Weary (1979) compared ~28,000 rabbit tests to ~143,000 LAL tests
LAL: 37 samples had unacceptable levels
of endotoxin
Rabbit pyrogen test only detected
endotoxin in 4 samples
And no LAL false negatives
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LAL and USP Pyrogen Test
• LAL more sensitive
Use of live animals (in vivo) causes
variability in test results
• LAL detects sub-pyrogenic amounts of endotoxin
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Manufacture of LAL
• Collect animals
• Extract blood
• Centrifuge blood
• Wash cells
• Lyse cells
• Extract proteins
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Horseshoe Crab Collection
• Handling with
care maximizes
survival rate
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ACC Manufacturing
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ACC Manufacturing
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Manufacture of LAL
• QC release
Determine sensitivity
6-hour test for quality/negative
background
pH
Test for sterility
Test for moisture
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Manufacture of LAL
• Labeling
• Submission to and release by theFDA
• Product sales
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FDA Licensed Products
LAL (Limulus Amebocyte Lysate)
TRADENAME
Chromo-LAL
Pyrochrome®
Chromogenic
Pyrotell®
-TTurbidimetric
Pyrotell®
STV
Pyrotell®
Multitest
Gel Clot
METHOD
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Endotoxins
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Pyrogen
• A substance that produces a fever when injected into blood or cerebrospinal fluid
Endotoxin
• A pyrogen in the cell wall of Gram-negative bacteria
Lipopolysaccharide (LPS)
• Chemically purified endotoxin
Definitions
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What is Endotoxin?
� A lipo-polysaccaride structural component of gram (-) bacterial cell wall
� An Immunomodulator that can cause:
fever, inflammation, headaches, nausea, chills,
vomiting, hypotension, lung toxicity, etc… &
death.
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Outer
Membrane
Inner
Membrane
“Double-track”
Bacteria
Electron micrograph of Gram-negative rod
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LPS Properties
• Polysaccharide
- Hydrophilic
• Lipid A
- Hydrophobic
• Negatively charged
- Non-specific adsorption
- Hydrophobic interaction
• Hydrophobic interactions form micelles, etc. stabilized by charge neutralization
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•Dry heat
•Base hydrolysis
•Oxidation
Lipid A
Endotoxin
Depyrogenation: the removal or destruction
of pyrogens, particularly endotoxin
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Physical DepyrogenationDry Heat
• 170oC for 2 hours (sterilization)No endotoxin destruction
• 180oC for 3 hours (depyrogenation)Endotoxin destruction
• 250oC for 30 minutesEndotoxin destruction
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Always Remember
• Sterile
Doesn’t mean depyrogenated
• Pyrogen-free
Doesn’t mean no pyrogens
• Dry Heat
Most effective depyrogenation
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Chelating agents
Acid or base
Surfactants
Charged/hydrophobic
proteins
Endotoxin
Variously sized aggregates (particles)
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Endotoxin
Biological Activity:(in blood or cerebrospinal fluid)
• Vomiting
• Hypotension
• Lung toxicity
• Abortion
• Fever
• Headache
• Chills
• Nausea
• Death
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Human Threshold Pyrogenic Doses
• Greiseman and Hornick (1969) Pyrogenicity of different organisms
Organism Pyrogenic Dose (ng/kg)
Salmonella typhosa 0.1 - 0.14
Escherichia coli 1.0
Pseudomonas sp. 50 - 70
Endotoxin
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• Endotoxin Unit (EU) is a unit of biological activity
• 1 EU = 1 IU (International Unit)
• EU is defined for the reference standard endotoxin (RSE) and must be measured for any other endotoxin
Endotoxin
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• Parenteral drugs:
5 Endotoxin Units/kg body weight/hour
350 EU/adult/hour
• Intrathecal drugs:
0.2 EU/kg/hr
14 EU/person/hour
Endotoxin Limits
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Medical devices
• 20 EU/unit or 200 EU/unit (worst case) if
device rinses are pooled for testing
Large volume parenterals
• (700mL/person/hr) = 0.5 EU/mL
USP Water for Injection
• 0.25 EU/mL
Endotoxin Limits
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Limulus Amebocyte Lysate (LAL) Test Methods
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Limulus Amebocyte Lysate
• Extract from blood cells ofLimulus polyphemus
• Clots in the presence of endotoxin in vitro
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Limulus Amebocyte Lysate
• Lyophilized blood cell lysate
• Complex mixture of proteins
Four involved in the clotting cascade
• Engineered to increase natural sensitivity
Formulated with salts, fillers, and buffers
for each specific method
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Biochemical Cascade
Gelation
Coagulogen Coagulin
Endotoxin
Factor B Factor G
Clotting Enzyme
Activated Factor(s) B/G
Activated Clotting Enzyme
Factor C Activated Factor C β-Glucan
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LAL Test
• Gel Clot
• Turbidimetric
• Chromogenic
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Setting up the test
1:1 1:2 1:40.1 mL LRW
0.1 mL sample
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Setting up the test
Test volume is 0.1mL
Add 0.1mL LAL reagent
Mix thoroughly
Incubate immediately
Discard 0.1mL to maintain equal volumes
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Reading the Gel-Clot Test
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LAL Method: Gel Clot
• Low equipment cost
• USP compendial method
• Resilient
• Fewer “outliers”
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Photometric Methods
• Chromogenic
λ = 0.005 EU/mL
• Turbidimetric
λ = 0.001 EU/mL in tube reader
λ = 0.005 EU/mL in plate reader
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Two Testing Methods
• Endpoint
An LAL test that is read once at the end of a set incubation period
• Kinetic
An LAL test that gathers data in short intervals throughout a variable incubation period
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Kinetic Method
Opticaldensity
Time
Threshold OD
0.25 EU/ml
0.125 EU/ml
0.0625 EU/ml
0.03125 EU/ml
0.5 EU/ml
Onset time
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Standard Curve (Kinetic Test)
Log
10(o
nse
t tim
e)
Log10(endotoxin concentration)
R ≥≥≥≥ 0.980
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Endpoint Method
• Absorbance (optical density) measured
after fixed incubation period
• Standard curve
OD vs. endotoxin concentration
• Limitations
Limited range
More technician time involved
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Turbidimetric Methods
• Coagulin molecules coalesce and cause increasing turbidity
• The rate of increase in turbidity is a function of endotoxin concentration
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LAL Method: Turbidimetric
• Most sensitive 0.001 EU/mL
• Broad range 10 - 0.001 EU/mL
• Temperature control and timing
• Plate reader or tube reader option
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Pyros KinetixTM
• 96 wells
• Small volume
λ = 0.001 EU/mL in tube reader
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• Color intensity indicates endotoxin levels
• Synthetic peptide
Amino acid sequence mimics natural
coagulogen:
BOC-Leu-Gly-Arg-CONH- -NO2
• Intact synthetic substrate is colorless
Chromogenic Reaction
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• Clotting enzyme recognizes synthetic substrate amino acid sequence and cleaves
• Paranitroaniline (pNA) released
• Free chromophore is yellow
The Chromogenic Reaction
H2N- -NO2
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Kinetic Chromogenic Method
• The rate of increase in optical density is a
function of endotoxin concentration
• Onset times are calculated using an
arbitrary threshold OD
• Standard curve
log10(onset time) vs. log10 (endotoxin
concentration)
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ELX808 Microplate Reader
• λ = 0.005 EU/mL
• 4 Zone Temperature control
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Select a Method: Chromogenic?
• Kinetic:
Sensitivity
0.005 EU/mL
Broad range
50 – 0.005 EU/mL
Rapid assay set-up
Instrumentation flexible
Use in other assays
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BET Overview
• LAL Test Validation
– Confirmation of labeled sensitivity
– Qualification of technician/laboratory
– Determine potency of control standard
endotoxin (CSE)
– Inhibition/Enhancement
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BET Overview
• Inhibition/enhancement test
– Does product affect test sensitivity?
– Compare sensitivity in water to the
sensitivity in sample
– Sample can be extract, rinse, or flush
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BET Overview
• Routine Test of a Validated Product– Release Test
– Sample preparation same as validated conditions
– Use validated dilution or dilution up to the MVD
-
-
+
+
1:16 PPC
Repl. 1
Repl. 2
0.25
+
+
-Ctrl
-
-
λ = 0.125 EU/mL
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Medical Device Challenge
• LAL tests
- Aqueous samples
• Device
-Solid, gauze, gel, liquid, etc.
• Sample
- Extraction
- Rinse
- Flush
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LPS Properties
• Aggregated
- MW in millions
– Salt solutions
– Divalent cations
– Acid pH
• Disaggregated:
- Monomers MW
2,500 - 25,000 Da
– Surfactants
– Chelating agents
– Basic pH
– Proteins, antibodies
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LPS Properties
Polymyxin B
molecules
neutralize LPS
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LPS Properties
Structural implications:
• Affinity for device surfaces
• Difficult to remove
– Unlikely to wash off unless rinse solution has greater affinity
• Surface shear useful
- Agitation
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Define Test Sample
• FDA sampling protocol – Lot sizes <30, test 2 units
– Lot sizes <100, test 3 units
– Lot sizes >100, test 3% • Maximum of 10 units
• USP sampling protocol- Not less than 3 and not greater than 10 units
• Grouped by common chemical formulation
ANSI/AAMI ST72:2002
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Define Test Sample
• Select devices with greatest exposure to tissue/body fluid- Non-pyrogenic fluid pathway
- Non-pyrogenic device
• Test entire unit?- Kit?
- Disassembled
- Cut pieces
• Endotoxin is not evenly dispersed
- Localized contamination
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Define Extraction Protocol
• Extraction of critical surfaces
• Rinse
• Flush
• Define protocol and composition of extraction fluid- Validate fluid, if not LRW
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Extraction Fluids
• LRW– Least interference
– Standard solution for LAL test
• Saline– LAL interference
– Least likely to recover endotoxin
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Extraction Fluids
• Surfactant/Detergent; <0.1%
– LAL interference
– Better endotoxin recovery
• Human Serum Albumin; <0.1%
– Minimal LAL interference
– Better endotoxin recovery
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Qualify Materials
• Materials contacting device should be
– Free of detectable endotoxins
– Sterile
– Free of interfering substances
• Examples of materials
– Containers, Manostat tubing, syringes,
forceps
– Aluminum foil, Parafilm strips, gloves(?)
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Recommended Rinse Protocols
• Derived from pyrogen tests
• FDA guideline: Extract for one hour with fluid at room temperature (>18°C) or for 15 minutes with fluid at 37°C
• USP: Initiate extraction with fluid at 37°C and extract for one hour at room temperature
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Perform Preliminary Tests
• Measure endotoxin in sample– Use different sampling protocols
– Test enough lots to establish level of uniformity of contamination within & between lots
• Inhibition/enhancement test– Gel-clot: sample dilution free of
endogenous endotoxin
– Photometric methods: do not require “clean” sample
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Endotoxin limit in the extract
K x N
V
K = tolerance limit expressed per device unit
N = number of samples pooled
V = total volume of pooled extracts
Limits for Medical Devices
=
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Limits for Medical Devices
• FDA guideline
- Maximum 10 units/lot
- Example:
Limit = (20 EU/unit) x (10 units)
400 mL
= 0.5 EU/mL
• 10 units, non-intrathecal
• Extract 40 mL fluid/unit
K x N
V
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Limits for Medical Devices
Another example: (non-intrathecal)
• 10 units
• Extract 1.0 mL fluid/unit
Limit = (20 EU/unit) x (10 units)
10 mL
= 20 EU/mL
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Limits for Medical Devices
• 5 units
• Extract 20 mL fluid/unit
• Intrathecal Device
Limit = (2.15 EU/unit*) x (5 units)
100 mL
= 0.1 EU/mL
* FDA guideline states 2.4 EU/unit
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Strategies
• Concentrate endotoxin in sample– At MVD?
- Large extraction volume?
- Interference?
• Ultrafiltration/diafiltration - Concentrates endotoxin and/or removes low
MW interfering substances
- Filter membrane, cartridge interference
– Solutes may affect endotoxin MW
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Inhibition/Enhancement Test
• Compare LAL sensitivities
• LRW standard series
• Sample standard series
• USP
- Four replicates sample standard series
- Two replicates water standard series
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Inhibition/Enhancement Test
• Endpoints must each be within twofold of
the labeled sensitivity of the LAL reagent
--+++
---++
-
-
LRW
--++
---+
λ/4λ/2λ2λ
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Inhibition/Enhancement Test
Is this test valid?----+
----+
----+
----+
- ctrlλ/4λ/2λ2λ
CSE (EU/mL) in sampleCSE (EU/mL) in LRW
---++
---++
- ctrlλ/4λ/2λ2λ
Slight inhibition
Valid test
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Extraction Validation
Reference:
• Bacterial Endotoxin Testing: A Report on the Methods, Background, Data, and Regulatory History of Extraction Recovery Efficiency (2004)
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Extraction Validation
Confirm that the extraction validation works• Challenge device with known amount of endotoxin
• Perform extraction protocol
• Perform LAL test
• Calculate recovery
• If recovery is low, modify limits and/or protocol
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Enhancement
• Beta-glucans (polysaccharides with
β−linkages sugar molecules)
– fungi, algae: 1,3-beta-D-glucans
– cellulose: 1,4-beta-D-glucans
• LAL-Reactive Material (LRM) described in hemodialyzer rinses
– Cellulose monoacetate, cellulose
diacetate, saponified cellulose acetate
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Beta-Glucans
Gelation
Coagulogen Coagulin
Endotoxin
Factor B Factor G
Clotting Enzyme
Activated Factor(s) B/G
Activated Clotting Enzyme
Factor C Activated Factor C β-Glucan
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Beta-Glucans
• Non-pyrogenic
• Synergistic with endotoxin
– Low and high molecular weights
– Variable structure
• Some structures are biologically active immunomodifiers
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Glucatell®
• (1→3)-β-D-glucan quantification (pg)
• Chromogenic method
• Verify false positives
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Glucashield™
• LAL insensitive to glucans
• 1,000 ng /mL Pachyman
• Buffer
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Conclusion
• 1977 FDA approved LAL test for release of medical devices
• Most devices are very straight-forward– Water rinses
– No interference
– Endotoxin recovered from challenge
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Conclusion
• Knowledge of product composition and
endotoxin characteristics provides an edge
• Problem Samples
- Antibacterial coatings
- Collagens
- Substances with a high affinity for endotoxin
• Preliminary characterization
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References
• Manufacturer’s product insert(s)
• USP Bacterial Endotoxins Test (BET) <85>
• “Guideline on Validation of the Limulus
Amebocyte Lysate Test as an End-Product
Endotoxin Test for Human and Animal
Parenteral Drugs, Biological Products, and
Medical Devices,” FDA, 1987
http://www.fda.gov/CBER/gdlns/lal.pdf
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References
• ANSI/AAMI ST72:2002
• Transfusion and Infusion Assemblies and
Similar Medical Devices, <161> USP
• Bacterial Endotoxin Testing: A Report on
the Methods, Background, Data, and
Regulatory History of Extraction Recovery
Efficiency (2004)
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Associates of Cape Cod, Inc.
Laurie Fife