Results of 1-year screening of donors in The Netherlands for human T-lymphotropic virus (HTLV) type I: significance of Western blot patterns for confirmation of HTLV infection.

BACKGROUND

Between January 1993 and January 1994, Dutch blood banks screened approximately 674,000 volunteer donors for the presence of antibodies to human T-lymphotropic virus type I (HTLV-I).

STUDY DESIGN AND METHODS

Confirmatory testing was performed on samples from 870 different anti-HTLV-I-reactive donors (0.13% of the total tested).

RESULTS

According to the authors' Western blot (WB) interpretation criteria, 15 (0.002%) donors tested HTLV-I-positive in the WB; 201 tested negative, and 654 (75% of donors reacting on enzyme-linked immunosorbent assay) tested indeterminate. Fresh samples from 234 of 870 anti-HTLV-reactive donors were tested for HTLV-I and type II (HTLV-II) DNA by polymerase chain reaction: all 15 WB-positive donors tested positive for HTLV-I DNA; 206 WB-indeterminate and 13 WB-negative donors tested negative for HTLV-I and -II DNA. Application of the manufacturer's (World Health Organization-based) guidelines for WB interpretation would have resulted in the misclassification of 48 (23%) of 206 polymerase chain reaction-negative donors as HTLV-I/II-positive. Risk factors were present in 14 of 15 HTLV-I-infected donors: 8 had a partner from an HTLV-I-endemic area, 4 were from HTLV-I-endemic countries, and 2 had received blood transfusions.

CONCLUSION

HTLV-I and -II infection is rare among Dutch blood donors. HTLV screening will prevent few cases of HTLV-related disease, but it will prevent a further spread of the virus by transfusion. In a low-risk population, conservative guidelines for WB interpretation unnecessarily generate an excess of false-positive results.