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

Abstract

Introduction: Connective 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.

Method: The 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.

Results: The 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.

Conclusions: For 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.

Keywords: Activated partial thromboplastin time; Connective tissue disease; Deep venous thrombosis; Systemic lupus erythematosus; Systemic sclerosis; Venous thromboembolism.