APTT: A screening test for hypercoagulability in type 2 diabetes mellitus patients

Abstract

Background: Thrombosis is a common complication in Type 2 Diabetes Mellitus (T2DM). Prolonged APTT values have clinical relevance as an indicator of factor deficiency or the presence of coagulation inhibitors. However, there is mounting evidence that shortened APTT values in some cases may reflect a hypercoagulable state, which is potentially associated with increased thrombotic risk and adverse cardiovascular events. We set out a cross-sectional study to measure the haemostatic profiles of T2DM patients and to determine the suitability of PT-APTT as markers for hypercoagulability in T2DM patients using VWF as a gold standard.
Methods: PT, APTT, VWF and Fibrinogen concentrations were measured in 213 T2DM patients and 172 non-diabetic healthy participants. VWF was used as a proxy marker for hypercoagulability in T2DM patients. Participants with VWF of >2.0 IU/ml , PT and APTT less than 11 and 30 seconds respectively, were regarded as being in hypercoagulable state.
Results: The results revealed that mean fibrinogen concentration for T2DM patients (4.3 ±2.5g/l) was significantly higher than control participants (2.3±1.6 g/l); P-value = 0.003.The mean Vonwillebrands factor concentration for T2DM patients (7.4 ±4.1 IU/ml) was significantly higher than control participants (2.6±2.2 IU/ml). P-value = 0.0004. The mean Prothrombin Time for T2DM patients (12.4±3.3 seconds) was lower than control participants (12.5 ±2.9 seconds) but the difference was not significant P-value = 0.168. The mean APTT for T2DM patients (24.7 ±3.8seconds) was significantly lower than control participants (32.2±4.2seconds). P value = 0.000. The study further revealed that APTT tests were more sensitive 93.7% (95% CI [88.0-96.7)] than PT test which had a sensitivity of 55.6% (95% CI [46.8- 63.9)]. Both APTT and PT tests had better specificity; however APTT was higher 95.4% (95% CI [88.8-98.2]) than PT test 90.8% (95% CI [82.9-94.3]). APTT test had a higher PPV 96.7% (95% CI [91.9-98.7)] than PT test 89.7% (95% CI 81.0 94.7]). PT test gave a much lower NPV 58.5% (95% CI [50.0-66.5]) as compared to APTT tests which had a higher NPV 91.2% (95% CI [83.6- 94.5]).
Conclusion: Haemostatic profile results show that T2DM patients are more hypercoagulable than non-diabetic healthy individuals. APTT had a better diagnostic specificity and sensitivity than PT. It is cheaper, easier to do and has high PPV and NPV compared to PT. APTT could therefore be used as a marker for hypercoagulability in T2DM patients.

Key words: Hypercoagulability, VWF, Type 2 diabetes mellitus, APTT, NPV, PPV