Discrepancy between human T-cell lymphotropic virus type I screening test and confirmatory tests in non-endemic areas

The purpose of this study was to examine the seroprevalence of human T-lymphotropic virus (HTLV)-I among pregnant women at our institution in Tokyo, Japan, which is a non-endemic area, and to investigate the results of Western blotting among pregnant women who had obtained positive results from a screening test.

The seroprevalence of HTLV-I was retrospectively reviewed in 11,352 pregnant women who gave birth at the National Center for Child Health and Development in Tokyo, Japan, between 2002 and 2009. For the screening test, a chemiluminescent enzyme immunoassay was performed followed by a confirmatory Western blot test.

The overall positive rate for the screening test was 0.33% (37/11,352). Western blot testing was performed in 36 of these 37 cases. Only nine patients (25%) were positive for HTLV-I by Western blot testing, seven patients (19%) were indeterminate, and 20 patients (56%) were negative.

In this study (carried out in a non-endemic area), the percentage of patients with a positive result from the screening test who were confirmed to be true carriers was significantly low, differing from endemic areas.