The clinical significance of a shortened activated partial thromboplastin time in patients with connective tissue disease.

introductionConnective tissue disease (CTD) patients have been reported to have an increased risk of venous thromboembolism (VTE). Deep venous thrombosis represents a potential emergency that may have a fatal outcome. The D-dimer test is the most widely accepted screening marker for VTE; however, elevation of the plasma D-dimer level without demonstrable thrombosis sometimes accompanies CTD activity itself, infection, and other conditions. Thus, the accuracy of a diagnosis of VTE based on a D-dimer test result is lower in CTD patients. The activated partial thromboplastin time (APTT) test is a very common and simple test.

methodThe medical records of 535 CTD patients were retrospectively investigated. The following data were extracted: APTT, D-dimer, thrombotic events, laboratory data, and systemic corticosteroid therapy.

resultsThe rates of thrombotic events and VTE were significantly increased in patients with a shortened APTT (< 26 s) (PSAPTT) in comparison to those without a shortened APTT (p = 0.004, 0.0009, respectively). The number of PSAPTTs was significantly increased in patients with VTE in comparison to those without VTE (p = 0.0009). In the diagnosis of VTE in CTD patients, the specificity and positive predictive value (PPV) of the D-dimer test were 71.6% and 83.8% and 12.7% and 19.4%, respectively. The combination of a shortened APTT and elevated plasma D-dimer level improved the specificity and PPV to 94.7% and 97.3% and to 25.0% and 36.4%, respectively.

conclusionsFor the evaluation of possibility of accompanying VTE in CTD patients, APTT shortened was useful and should be evaluated with careful attention. KEY POINTS: • Regarding the specificity for diagnosing VTE in CTD patients, a shortened APTT showed a value (84.3%) comparable or superior to that of the D-dimer test. • The combination of a shortened APTT and elevated D-dimer level improved the specificity of the diagnosis of VTE in CTD patients to (94.7% or 97.3%) in comparison to the D-dimer test alone (71.6% or 83.8%). • The positive predictive value of the combination of a shortened APTT and plasma D-dimer elevation for the diagnosis of VTE in CTD patients increased to 25.0% or 36.4%. • In the management of CTD patients, physicians should pay attention when they encounter patients with a shortened APTT, as it may indicate VTE.