Prevalence of short partial thromboplastin times in a military treatment facility

It was recently noted that a shortened activated partial thromboplastin time (aPTT) is associated with increased venous thromboembolic events. The prevalence of aPTT shortening remains unknown.

We conducted a retrospective analysis of aPTT results over a 2-month period. These results were not associated with patient clinical information.

We obtained 3,376 aPTT samples, which were analyzed in groups: <25.0, 25.0-35.0, and >35.0 seconds (two standard deviations from our laboratory's normal values). Eighty-six samples had aPTT<25 (8.5%), 2,026 samples between 25.0-35.0 (60.0%), and 1,064 samples>35.0 (31.5%). Using chi-square goodness-of-fit, we found a clinically significant greater-than-expected prevalence of low aPTT levels (p<0.001).

Although elevated aPTT samples could be explained by anticoagulation therapy, the reason for our findings of an increased number of low-aPTT studies remains unexplained. Further studies are required to investigate the clinical correlation of low aPTT levels and the incidence of venous thromboembolic events (VTEs) in our population.