Evaluation of a rapid lateral flow immunoassay (STic Expert HIT) for the diagnosis of heparin-induced thrombocytopenia (HIT)

Transcription

1 Evaluation of a rapid lateral flow immunoassay (STic Expert HIT) for the diagnosis of heparin-induced thrombocytopenia (HIT) Liesbeth De Cooman and Katrien Devreese University Hospital Ghent Coagulation Laboratory 1

2 HIT: introduction! Heparin Induced Thrombocytopenia (HIT)! Thrombocytopenia due to administration of heparin! Predisposes to thrombosis! Mechanism: antibodies against heparin/pf4 complexes that activate platelets 2 2

3 HIT: introduction Heparin PF4 PF4 an,bodies HIT FcγIIa receptor Platelet Platelet ac,va,on Forma,on of micropar,cles Forma,on of blood clots 3 3

4 HIT: introduction! Diagnosis is based on clinical and laboratory data! Warkentin 4T scoring system to assess risk (low, intermediate and high risk)*! Most laboratory tests are time consuming and need skilled laboratory staff! Quick and reliable diagnosis may improve patient outcome! Study: evaluation of a rapid lateral flow immunoassay and an ELISA detecting IgG HP4 antibodies *Greinacher A. and Warkentin T.E. Thrombosis Research. 2006: 118,

5 Asserachrom HPIA IgG! Asserachrom HPIA IgG (Diagnostica Stago)! ELISA detecting anti-pf4/heparin antibodies (IgG)! Results within app. 3 hours! Quantitative result (OD) qualitative result with the aid of a calculated cut-off per batch 5 5

6 STic Expert HIT! STic Expert HIT (Diagnostica Stago)! Rapid IgG specific lateral flow immunoassay! Quick screening test! Add 5 µl sample (serum) in the well of the test cassette! Add 2 drops of sample buffer! Incubate 10 minutes at room temperature! Visual evaluation by provided Evaluation Card Picture adapted from Diagnostica Stago 6 6

7 Study design! Evaluation of the performance of Asserachrom HPIA IgG and STic Expert HIT as immunological assay for HIT! 153 citrated plasma samples (stored at -80 C) of patients suspected with HIT! Results for STic Expert HIT were read by 3 blinded readers! Results were confirmed by a CD62p flowcytometric functional assay*! Determination of test sensitivity, specificity, PPV, NPV for both tests and inter reader agreement (kappa) for STic Expert HIT *Denys B et al. Thrombosis Research. 2008: 123, Tomer A. British Journal of Haematology. 1997: 98, Tomer A. et al. American Journal of Hematology. 1999: 61,

8 Study results Low risk 4T score Intermediate risk high risk CD62p nega;ve posi;ve Pre- test probability (%) 4T score Low R (54/2) Intermediate R (58/9) High R (21/9)

9 Asserachrom HPIA IgG: results flow CD62p posi;ve nega;ve Asserachrom HPIA IgG OD 0,236* OD < 0, flow CD62p posi;ve nega;ve Asserachrom HPIA IgG OD 1, OD < 1, Asserachrom HPIA IgG Cut- off OD = 0,236* Cut- off OD = 1,0 Sensi;vity (%) [ ] [ ] Specificity (%) [ ] [ ] LR [ ] [ ] LR [ ] PPV (%) [ ] [ ] NPV (%) [ ] [ ] *Cut- off OD calculated for each run according to manufacturer's protocol; mean cut- off OD 0,236 ROC curve analysis ideal cut- off OD 9 9

10 STic Expert HIT : results Low risk 4T score Intermediate risk High risk Reader 1 nega;ve posi;ve Reader 2 nega;ve posi;ve Reader 3 nega;ve posi;ve Kappa R2 R3 R R Overall Fleiss kappa agreement:

11 STic Expert HIT : results Reader 1 flow CD62p Reader 2 flow CD62p Reader 3 flow CD62p posi;ve nega;ve posi;ve nega;ve posi;ve nega;ve STic Expert posi;ve 19 STic Expert posi;ve S;c Expert posi;ve nega;ve 1 nega;ve nega;ve STic Expert STic Expert STic Expert Sensi;vity (%) [ ] Sensi;vity (%) [ ] Sensi;vity (%) [ ] Specificity (%) [ ] Specificity (%) [ ] Specificity (%) [ ] LR [ ] LR [ ] LR [ ] LR [ ] LR [ ] LR [ ] PPV (%) [ ] PPV (%) [ ] PPV (%) [ ] NPV (%) [ ] NPV (%) [ ] NPV (%) [ ] 11 11

12 STic Expert HIT : results 1/3 scores posi;ve Post- test probability (%) S;c Expert HIT Pre- test probability (%) Nega;ve Posi;ve Low R , (54/2) [ ] [1,84-48,26] Intermediate R (58/9) [ ] [ ] 4T score High R (21/9) [ ] [ ] 2/3 scores posi;ve Post- test probability (%) S;c Expert HIT Pre- test probability (%) Nega;ve Posi;ve Low R (54/2) [ ] [ ] Intermediate R (58/9) [ ] [ ] 4T score High R (21/9) [ ] [ ] 3/3 scores posi;ve Post- test probability (%) S;c Expert HIT Pre- test probability (%) Nega;ve Posi;ve Low R (54/2) [ ] [ ] Intermediate R (58/9) [ ] [ ] 4T score High R (21/9) [ ] [ ] 12 12

13 STic Expert HIT : discussion Reader 1 flow CD62p Reader 2 flow CD62p Reader 3 flow CD62p posi;ve nega;ve posi;ve nega;ve posi;ve nega;ve STic Expert posi;ve 19 STic Expert posi;ve S;c Expert posi;ve nega;ve 1 nega;ve nega;ve STic Expert STic Expert STic Expert Sensi;vity (%) [ ] Sensi;vity (%) [ ] Sensi;vity (%) [ ] Specificity (%) [ ] Specificity (%) [ ] Specificity (%) [ ] LR [ ] LR [ ] LR [ ] LR [ ] LR [ ] LR [ ] PPV (%) [ ] PPV (%) [ ] PPV (%) [ ] NPV (%) [ ] NPV (%) [ ] NPV (%) [ ] 13 13

14 STic Expert HIT : discussion! 1 false negative result (citrated plasma sample, -80 C)! Same case missed by the 3 readers! non-orthopedic surgerical patient! LMWH! 4T score of 3 (low risk)! OD of

15 STic Expert HIT : discussion! 1 false negative result! Same case missed by the 3 readers 15 15

16 STic Expert HIT : discussion! 1 false negative result (citrated plasma sample, -80 C)! Same case missed by the 3 readers! Analysis was repeated by! A different test performer! 3 different, blinded readers Same false nega,ve result 16 16

17 STic Expert HIT : discussion 17 17

18 Conclusion! Asserachrom HPIA IgG + Excellent sensitivity (100%) and good specificity (80.45%) - More time consuming! STic Expert HIT + Quick method + Easy to use + Good sensitivity (95.00%) and specificity (83.96%) - In our study no 100% sensitivity/npv for citrated plasma samples stored at -80 C 18 18

19 Special thanks to! Coagulation Laboratory, University Hospital Ghent! Prof. Dr. Devreese! Sylvie Mulliez! Michael Luypaert! Stago 19 19