Survey Report 2010-4 LA.pdf - NASCOLA

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ECAT FOUNDATION EXERCISE 2010-4 INTERNATIONAL EXTERNAL QUALITY ASSESSMENT Page 2 of 11 PROGRAMME IN HAEMOSTASIS AND THROMBOSIS Print date: 28 February 2011 Copyright © 2010 ECAT Foundation Labcode: 900 Mixing tests For the mixing tests the APTT and dAPTT showed in 38% and 60% of the cases, respectively, a prolonged test result. The table below showed again for the most frequently used APTT reagents the classification. MIXING Normal (%) Borderline (%) Prolonged (%) APTT SP (IL) 86% 9% 5% HemosIL SynthASil (IL) 100% 0% 0% Pathromtin SL (Siemens) 61% 38% 11% Actin FSL (Siemens) 46% 27% 27% PTT Automate / STA APTT (Stago) 17% 25% 58% PTT LA (Stago) 19% 9% 72% From this table it is clear that the majority of users of the indicated Stago reagents classified this sample in the mixing test borderline or prolonged. For the indicated Siemens reagents an intermediate pattern was observed, while the vast majority of the users of the indicated I.L. reagents classified the sample as normal in the mixing test. Confirmation test A positive confirmation test was almost only observed in the APTT and dAPTT assay groups (46% and 47%, respectively). The most frequently used APTT-based confirmation test are Siemens Actin FS (n=21) and Stago Staclot LA (n=49). For Actin FS 24% classified the test as positive and 14% as borderline. For the Staclot LA test this is 86% (!) and 6%, respectively. Conclusion These findings show that, depending on the method used, a false positive Lupus Anticoagulant test could be observed using an APTT based assay system. The ISTH criteria indicate that when at least one of the test systems used showed a positive lupus test the sample should be identified as Lupus Anticoagulant positive. In the case of a sample with an elevated CRP level this could lead to a falsely positive classified sample.
ECAT FOUNDATION EXERCISE 2010-4 INTERNATIONAL EXTERNAL QUALITY ASSESSMENT Page 3 of 11 PROGRAMME IN HAEMOSTASIS AND THROMBOSIS Print date: 28 February 2011 Copyright © 2010 ECAT Foundation Labcode: 900 Overview ratio ECAT plasma / normal plasma RATIO SCREENING n mean CV Range APTT 253 1.43 16.8% 0.69 – 2.12 APTT SP (IL) 32 1.24 8.1% 1.06 – 1.40 HemosIL SynthASil (IL) 14 1.16 6.4% 1.06 – 1.33 Pathromtin SL (Siemens) 24 1.35 8.1% 1.13 – 1.56 Actin FSL (Siemens) 42 1.39 10.1% 0.99 – 1.74 PTT Automate / STA APTT (Stago) 24 1.71 9.9% 1.24 – 2.12 PTT LA (Stago) 71 1.66 9.0% 1.21 – 1.95 DRVVT 289 1.02 10.8% 0.79 – 2.10 DVVtest (AD) 18 0.96 9.6% 0.82 – 1.17 LAC screen (I.L.) 66 1.07 10.3% 0.91 – 1.59 LA screen (Life Diagnostics) 26 1.03 8.5% 0.88 – 1.19 LA check (Precision Biologic) 15 0.96 7.1% 0.79 – 1.08 LA1 screen (Siemens) 105 1.00 13.0% 0.79 – 2.10 DRVVT Screen (Stago) 38 0.99 6.1% 0.89 – 1.21 KCT 22 1.05 26.7% 0.69 – 1.73 dAPTT 16 1.40 22.1% 0.95 – 2.08 dPT 24 1.04 10.6% 0.83 – 1.28 Innovin (Siemens) 11 1.03 9.7% 0.83 – 1.15 SCT 17 1.11 14.4% 0.80 – 1.48 Other 2 1.26 - 1.24 – 1.28 Remarks: The high CV of the dAPTT-group and KCT-group in comparison to the other assay groups is remarkable. The relatively high CV in the aPTT group in comparison to previous surveys is caused by the differences in sensitivity to CRP between the different reagents. Within a particular aPTT reagent group the CVs relatively low. RATIO MIXING n mean CV range APTT 204 1.21 14.0% 0.82 – 2.02 APTT SP (IL) 22 1.12 7.9% 0.82 – 1.25 Pathromtin SL (Siemens) 16 1.11 6.2% 0.99 – 1.24 Actin FSL (Siemens) 36 1.20 6.9% 0.99 – 1.38 PTT Automate / STA APTT (Stago) 24 1.34 10.4% 1.15 – 1.75 PTT LA (Stago) 69 1.32 13.6% 0.92 – 2.02 DRVVT 100 1.00 8.5% 0.77 – 1.59 LAC screen (I.L.) 17 1.04 14.4% 0.92 – 1.59 LA screen (Life Diagnostics) 10 0.98 4.7% 0.90 – 1.05 LA1 screen (Siemens) 45 0.99 6.3% 0.77 – 1.10 DRVVT Screen (Stago) 12 1.03 6.5% 0.94 – 1.21 KCT 19 0.96 12.5% 0.67 – 1.20 dAPTT 14 1.20 13.3% 0.99 – 1.59 dPT 12 1.03 7.1% 0.96 – 1.23 SCT 3 1.02 - 0.99 – 1.06 Other 1 0.97 - - Remarks: The relatively high CV in the aPTT group in comparison to other assay groups is caused by the differences in sensitivity to CRP between the different reagents. Within a particular aPTT reagent group the CV is in most cases relatively low.
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