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Feasibility of human T-lymphotropic virus type I screening using pooled sera
Chao-Sung Chang1, Ya-Wen Wu, Ya-Chun Pan
1Blood Bank, Kaohsiung Municipal Hsiao-kang Hospital, Kaohsiung, Taiwan.
Background And Purpose:
The human T-cell lymphotropic virus type I (HTLV-I) seroprevalence rate among volunteer blood donors in Taiwan is low. To study the feasibility of HTLV-I enzyme immunoassay (EIA) screening using pooled sera, we prospectively compared its sensitivity to that of the routine test for each donor.
Methods:
HTLV-I EIA tests for each serum sample and a pooled-sera test with 50 samples from voluntary donated blood samples were performed concurrently to assess the effectiveness and cost savings of this screening method.
Results:
Of 135,606 blood samples from volunteer donors tested for HTLV-I infection, 60 samples (0.044%) were HTLV-I EIA-positive using the routine method. Among these, the positive results were confirmed by Western blot in 22 samples (36.7%). In the pooled-sera test, 17 of 2,713 pooled samples were EIA-positive and these results were all confirmed by Western blot. Five of the 22 (22.7%) EIA-positive samples had a false-negative result in the pooled-sera test. Serial dilution in these five cases revealed that the maximum dilution before loss of sensitivity was 8-fold for two specimens and 16-fold for three specimens.
Conclusion:
In this study, the 50-pooled sera test had higher specificity (100%), but lower sensitivity (77.3%), than the routine HTLV-I screening. Our results suggest that use of a pooling method with five samples would leave a reasonable safety margin and be feasible for HTLV-I mass screening in areas with low seroprevalence for HTLV-I infection.