Academic journal article Bulletin of the World Health Organization

Evaluation of Commercial HTLV-1 Test Kits by a Standard HTLV-1 Serum Panel

Academic journal article Bulletin of the World Health Organization

Evaluation of Commercial HTLV-1 Test Kits by a Standard HTLV-1 Serum Panel

Article excerpt

INTRODUCTION

Human T-cell lymphotropic virus type 1 is the etiological agent of adult T-cell leukaemia (ATL)[1-3], HTLV-1-associated myelopathy (HAM/TSP)[4, 5] and other HTLV-1-associated diseases[6-8]. HTLV-1 infections are transmitted via breast-feeding, sexual contact, and blood transfusions[9]. Exclusion of HTLV-1-contaminated blood has decreased bloodborne transmission of HTLV-1 in Japan[10].

Anti-HTLV-1 antibody testing is useful for detecting infection with the virus, because HTLV-1-seronegative persons who are truly infected are rare[11, 12]. Thus, HTLV-1 test kits for the routine screening of blood donors have become available, but they do not always accurately determine the HTLV-1 status of an individual[13, 14].

In order to assess comparatively the various diagnostic assays for HTLV-1 infection that are currently available on the market, we investigated the sensitivity and specificity of particle agglutination (PA) and enzyme immunoassay (EIA) kits for HTLV-1 using the standard HTLV-1 serum panel that we have reported previously[15].

The results obtained indicated that most of the kits are sufficiently sensitive to screen for HTLV-1 antibodies, but that some EIA kits need to be optimized to increase their specificity.

Materials and methods

Standard HTLV-1 serum panel

The standard serum panel consisting of sera that were positive or negative for HTLV-1 (standard HTLV-1 serum panel) was established using samples from the HTLV-1 surveillance serum bank in Kagoshima, an HTLV-1-endemic area in southern Japan[15, 16]. The standard panel consisted of a set of 200 sera from individual asymptomatic HTLV-1 carriers (HTLV-1-positive sera) and 200 sera from healthy donors HTLV-1-negative sera).

The donors of HTLV-1-positive sera were initially screened using a first-generation PA test (lot 1) (SERODIA ATLA, Fujirebio Inc., Tokyo, Japan)[17] and the result confirmed by immunofluorescence test using MT-1 cells(3) and by the polymerase chain reaction (PCR) test for HTLV-1 proviral DNAs in their peripheral blood lymphocytes (PBL) using a primer set for the pX region[18, 19]. The HTLV-1-negative sera were obtained from normal healthy donors who had no risk of HTLV-1 infection and who were confirmed free of HTLV-1 infection by the serological and virological tests described above.

PA and EIA kits evaluated in the study

Two types of PA kits and nine types of EIA kits were evaluated in the study (Table 1). The PA kits were provided by United Biomedical Inc.(a) two different lots of the PHA-CHEK test), while Fujirebio(b) provided a second-generation PA kit (lot 2), which differed from the kit that we used previously[20]. The EIA kits were provided by nine manufacturers.(c) Two different lots of EIA kits were provided by Abbott Laboratories, Diagnostic Biotech Ltd., Organon Teknika Corp., and IAF BioChem International Inc.

[TABULAR DATA OMITTED]

The HTLV-1 antigens incorporated into the PA and EIA kits were from different virus strains and cell lines and differed also in their level of purification, as shown in Table 1. All the kits were in satisfactory condition on arrival in Kagoshima and were stored at 4 [degrees] C until they were tested.

The PA and EIA kits were tested according to the manufacturers' instructions and the sensitivity and specificity were evaluated using the HTLV-1-positive and HTLV-1-negative sera. The [delta]-value (mean [log.sub.10] [sample reading/cut-off value]/standard deviation) developed by Crofts et al.[21] was calculated for each EIA kit.

Results

The standard HTLV-1 serum panel

For the study we used the standard HTLV-1 serum panel that had been established using serological and virological methods at the WHO Collaborating Centre for Human Retroviral Infections associated with Neurological Disorders, Kagoshima University. We selected 200 HTLV-1 positive sera from 1309 asymptomatic HTLV-1 carriers who had been followed up by the HTLV-1 surveillance programme in Kagoshima prefecture since 1985[15]. …

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