Transient lupus anticoagulant associated with prothrombin deficiency: unusual cause of bleeding in a 5-year-old girl.

PURPOSE: We present the association of a lupus anticoagulant with hypoprothrombinemia in a 5-year-old girl, who presented with ecchymoses and a hematoma. This coagulopathy should be included in the differential of bleeding in the previously healthy children. PATIENTS AND METHODS: Coagulation and immunology laboratory evaluation was performed at the time of presentation with bleeding and 2 months later, after complete clinical recovery. RESULTS: A 5-year-old girl presented with ecchymoses and a hematoma after after an upper respiratory illness. Laboratory evaluation showed prolongation of both the prothrombin time (PT) and activated partial thromboplastin time (aPTT) due to the presence of a strong lupus anticoagulant associated with a decreased level of prothrombin (15 U/dl). Hypocomplementemia was also detected. Bruising resolved spontaneously, and the PT and aPTT gradually normalized. Reevaluation 2 months later showed that the lupus anticoagulant had disappeared and the prothrombin deficiency was markedly improved. CONCLUSIONS: This case demonstrates that transient lupus anticoagulants must be included in the differential for bleeding in young children. Also, in children with lupus anticoagulants, neither the association of hypoprothrombinemia nor the presence of evidence of activation of the immune system appears to predict whether a patient will have or develop systemic lupus erythematosus.

Artifactual prolongation of the activated partial thromboplastin time mimicking a coagulopathy. A lesson relearned.

A markedly prolonged activated partial thromboplastin time (APTT) was observed in a 61-year-old woman with bruising and a decreasing hematocrit. Coagulation laboratory evaluation was sought to determine the cause of the prolonged APTT and bleeding. Evaluation demonstrated that, rather than identifying a coagulopathy, the APTT prolongation was most likely artifactual. The APTT was actually very short. With a combination of a relatively strong activating APTT reagent (Dade Actin; Dade, Miami, FL) and a fixed lag phase in the automated coagulation instrument (16 seconds), the clot formed before the instrument began to read. Thus, during the period of observation (120 seconds), no change in optical density was observed. This was interpreted by the laboratory as "> 120 seconds." This case reminds those involved in the performance and interpretation of APTTs of the importance of a manual or visual method of verifying markedly prolonged APTTs.

Standardizing the prothrombin time. Calibrating coagulation instruments as well as thromboplastin.

Recently, indications for anticoagulation with warfarin have increased, prothrombin time (PT) monitoring at offices and homes has become available, and the international sensitivity index (ISI) has been recognized as a means of adjusting for differences in thromboplastins to standardize warfarin sodium dosing. However, different coagulation instruments may yield differences in PTs even after correcting for the ISI by means of the international normalized ratio (INR) (INR = [PT measured ISI/PT normal]). Because the PTs and INRs from our Anticoagulation Clinic (portable PT monitor, ISI = 2.04, normal PT = 12.0 seconds) differed from the hospital reference laboratory (ISI = 2.01, normal PT = 12.0 seconds) despite nearly identical ISIs and equivalent control or normal PTs, we systematically compared the two systems. During a 3-month period, we studied two groups of 50 consecutive patients who had been receiving a stable dose of warfarin. After a single venipuncture, PTs and INRs were measured independently, and regression lines were calculated. Within each group, the results from the different instruments were not identical, but they were highly correlated. In comparing INRs, the regression lines for the separate and combined groups were as follows: group 1 monitor INR = 0.49 reference INR + 0.81, r = .94; group 2 monitor INR = 0.57 reference INR + 0.86, r = .88; and combined monitor INR = 0.49 reference INR + 0.95, r = .89. Only 82% of the differences for all samples were within 1.0 INR units. We concluded that the instrumentation effect may be clinically meaningful, and coagulation instruments as well as thromboplastins should be calibrated to standardize warfarin therapy.