Prolonged aPTT after kidney transplantation due to transient lupus anticoagulants

After kidney transplantation, a renal biopsy may be needed to elucidate the reasons for lack of graft function. If the activated partial thromboplastin time (aPTT) is prolonged, the biopsy will often be postponed, as increased risk of bleeding must be expected. However, aPTT prolongation is not always due to lack of coagulation factors, but can be due to the presence of lupus anticoagulants (LAs). Clinical observations in our department indicated that a large proportion of recently kidney-transplanted patients developed prolonged aPTT values without clinical complications.

A prospective study of patients receiving a kidney transplant in 2004 was conducted to investigate the frequency and cause of prolongation of the aPTT.

Twenty-seven patients were included in the study; none had prolonged aPTT or LAs before the transplantation. In the post-transplantation period, 19 patients (70.4%) had a significantly prolonged aPTT. Further investigation showed that for all 19 patients, prolongation was due to acquired antibodies: 13 had developed LAs and six had developed unspecific antibodies. The acquired antibodies were transient and did not affect clinical outcome.

This is the first study investigating prolonged aPTT in the post-transplantation period. All patients with prolonged aPTT had acquired transient antibodies, i.e. LA or 'LA-like'. If a renal biopsy was requested, 70.4% of the transplanted patients would presumably have their biopsy postponed due to prolonged aPTT, but as LAs do not increase the risk of bleeding, such a delay would be unnecessary. Immediate LA investigation is therefore recommended if a recently transplanted patient requiring surgical procedures has a prolonged aPTT.