The Nijmegen modification of the FVIII inhibitor assay offers improved specificity and sensitivity over the original Bethesda assay. (Level 1) [ [9, 10] ] It is performed as follows: Buffered PNP (providing FVIII) is mixed with test plasma
and incubated at 37°C After 2 h, the residual FVIII is measured by comparison against the FVIII in a control mixture comprised of buffered PNP and FVIII-deficient plasma, which has been incubated alongside the test mixture. Residual FVIII is converted into inhibitor units using a semi-log plot of the residual FVIII against inhibitor convention, which has been constructed using the assumption that 100% residual = 0 BU mL−1 inhibitor, and 50% residual = 1.0 BU mL−1 (the latter being the internationally agreed convention for defining inhibitor activity). When residual FVIII activity is <25%, the patient plasma must be retested after dilution to avoid underestimation selleck compound of the inhibitor potency. An inhibitor titer of ≥ 0.6 BU mL−1 LY294002 chemical structure is to be taken as clinically significant
[11]. Even the simplest coagulation screening tests are complex by nature. A laboratory scientist/technologist with an interest in coagulation must have an in-depth understanding of the tests to achieve accurate results. In some cases, it may be beneficial to have a laboratory scientist/technologist who has had further training in a specialist center. Equipment and reagents are the tools of the trade of any laboratory. The
following requirements are necessary for accurate laboratory testing. A 37°C ± 0.5°C water bath. A good light source placed near the water bath to accurately observe clot formation. Stopwatches. Automated pipettes (either fixed or variable volume) capable of delivering 0.1 mL and 0.2 mL accurately and precisely. Clean soda glass test tubes (7.5 cm × 1.2 cm) for clotting tests. Reuse of any glassware consumables should be avoided whenever possible, unless it can be demonstrated that test results are unaffected by the process used. Plasticware used in coagulation analyzers should not be re-used. An increasingly large number of semi-automated and fully automated coagulometers are now available. In many cases, this equipment has the following advantages: Accuracy of end-point reading. Improved precision of test results. Ability to perform multiple clot-based assays. medchemexpress Reduction of observation errors (the end-point of the reaction is typically measured electromechanically or photoelectrically). Use of polystyrene (clear) cuvettes instead of glass tubes. All equipment requires maintenance to be kept in good working order. When equipment is purchased, consideration should be given to, and resources put aside, for regular maintenance by a product specialist. Pipettes should be checked for accurate sample/reagent delivery. Water baths, refrigerators, and freezers should undergo regular temperature checks.