Aplicación del tiempo de tromboplastina parcial activado (TTPA) con tiempo de incubación modificado en el diagnóstico del anticoagulante lúpico (AL)

Abstract

Although several tests are used to screen for the presence of LA, none detects all its types. The shortening of APTT observed when the pre-incubation period is prolonged, proved to be a sensitive test for the presence of LA. Material and methods: We determined the APTT, performed with a 4 or 15 min preincubation period (APTTs and APTT15 respectively), in 22 healthy subjects, 3 commercial positive controls for LA, 16 patients with a previous diagnosis of LA and 54 patients with recurrent fetal loss and/or infertility. Evidence of LA was established by a positive Staclot-LA test. Results: APTTs and APTT15 were 31.5±4.7 and 28.4±4.5 seconds respectively in samples from 22 normal subjects. The figures in samples with LA, were 71.5±20.3 s and 58.6±18 s respectively. The difference between the two APTTs performed on an individual sample was defined as the APTT 4-15 and was 2.6±2.0 in normal subjects 2.5±2.8 in 13 patients anticoagulated with warfarin, -10.0±6.5 in 13 patients receiving heparin, and 13.2±4.9 in 15 patients with LA. The test values for LA patients were significantly higher than those for normal subjects (p <0.0001). For values over 5, the APTT 4-15 had 93.3% sensitivity and 100% specificity. In one patient with recurrent fetal loss or infertility, who was LA positive, the APTT 4-15 was positive with a value of 14. Conclusions: This modified TTPA is easy to perform, and provides a reasonably discriminatory value for the presence of LA. Therefore, we recommend the TTPA 4-15 to screen for LA