Table 5:

Prediction of functional assay positivity across anti-PF4/heparin antibody level thresholds

Anti- PF4/heparin IgG OD Threshold	Sensitivity	Specificity	False Negatives	False Positives
0.4 (McMaster)	1	0.785	0	516
0.4 (Greifswald)	0.946	0.562	65	1451
0.4 (Tours)	1	0.555	0	283
1.0 (McMaster)	0.923	0.954	31	111
1.0 (Greifswald)	0.784	0.887	260	375
1.0 (Tours)	0.979	0.794	4	131
1.5 (McMaster)	0.825	0.982	70	43
1.5 (Greifswald)	0.549	0.966	543	112
1.5 (Tours)	0.892	0.893	21	68
2.0 (McMaster)	0.568	0.994	173	14
2.0 (Greifswald)	0.3865	0.989	738	36
2.0 (Tours)	0.763	0.962	46	24
2.5 (McMaster)	0.288	0.998	285	4
2.5 (Greifswald)	0.192	0.997	972	10
2.5 (Tours)	0.516	0.992	94	5
3.0 (McMaster)	0.025	1	390	0
3.0 (Greifswald)	0.0216	1	1177	0
3.0 (Tours)	0.227	0.997	150	2

Specificity and sensitivity calculated for optical density values in each cohort, including OD values currently implemented in HIT guidelines as demarcating for classifying patients as HIT negative (OD<0.4 units) or HIT positive (OD>2.0 units) in the absence of functional assay results. False negative and positive values are absolute counts for each cohort.