Thrombocytopoenia as marker for HIV exposure in the neonate.

Thrombocytopoenia is a well-described marker of human immunedeficiency virus type 1 (HIV) infection of children. After documenting thrombocytopoenia in a HIV-exposed neonate, who was subsequently shown not to be infected, we evaluated thrombocytopoenia (platelets < 150 x 10(9)/l) as a marker for HIV exposure in newborns. This is, to our knowledge, the first study of thrombocytopoenia in HIV-exposed neonates. A retrospective hospital-based descriptive study was performed over an 18-month period (July 1997-December 1998). Patients were recruited either through identification of known HIV-positive mothers or neonates with thrombocytopoenia who were then screened for HIV exposure. For eligibility, neonates with either HIV antibodies or direct evidence of infection (p24 antigenaemia or HIV RNA detected by polymerase chain reaction after 1 month of age) were included. Thirty-four HIV-exposed (HIV-ELISA positive) neonates were identified, of whom 16 (47 per cent) had thrombocytopenia. In 12 (35 per cent), no underlying cause other than HIV was identified. Nine thrombocytopoenic babies were infected and seven uninfected. Unexplained thrombocytopoenia, while an imperfect marker, should alert the physician to the possibility of HIV exposure. It does not necessarily imply HIV infection. A prospective study is recommended to evaluate further the sensitivity and specificity of this marker.