HTLV screening test
A total of 59,929 blood donations (Hebei: 16,144, Changsha: 15,164, Shenzhen: 28,621) were collected and screened for HTLV-1/2 using CLIA (Table 1). Among these, 115 were initially detected as reactive in ELISA and/or CLIA, of which one sample was only reactive in ELISA but non-reactive in CLIA; 109 donations were reactive in CLIA and non-reactive in ELISA, and 5 samples were detected as reactive in ELISA and CLIA (Fig. 2). After repeated testing, 33 blood donations (Hebei: 4, Changsha: 3, Shenzhen: 26) were identified as reactive for the HTLV antibody (Table 1). The repeated reactive results in CLIA and/or ELISA among donations in the Shenzhen blood center (0.0908%, 26/28,621) was higher than Hebei (0.0248%, 4/16,144) and Changsha (0.0198%, 3/15,164) (p < 0.05); no significant difference in serologic activity was found between Hebei and Changsha blood centers.
HTLV confirmatory test
Among the 33 reactive blood donations for HTLV-1/2 by L2400 and/or ELISA, 29 were confirmed as HTLV-1/2 negative, 3 were HTLV-1/2 indeterminate (Hebei: 2, Shenzhen: 1), and only one collected in Shenzhen was positive for HTLV-1 antibodies (Table 2). Among the 6 samples that were initially reactive in ELISA, one (16.7%, 1/6) was confirmed as HTLV positive and one (16.7%, 1/6) was indeterminate. Out of 32 samples detected reactive by CLIA, one was positive (3.1%, 1/32) and 2 samples (6.3%, 2/32) with indeterminate results were observed after the INNO-LIA test (Fig. 2). Indeterminate HTLV-1/2 samples in Hebei, Changsha, and Shenzhen blood centers consisted of 0.0124% (2/16,144), 0.0000% (0/15,164), and 0.0035% (1/28621) of the samples, respectively (p > 0.05). The true negative population percentage of HTLV-1/2 among blood donors in Hebei was 99.9752% (16,140/16,144), which was similar to Changsha (99.9868%, 15,162/15,164) and Shenzhen (99.9092%, 28,595/28,621) (p > 0.05). Furthermore, no statistical differences were observed in the HTLV-infected donors in the three blood screening laboratories (p > 0.05). In summary, of the 59,929 donations, 99.9933% (59,925/59,929) samples were confirmed as HTLV-1/2 negative, and 0.0050% (3/59,929) samples were classified as indeterminate for HTLV-1/2 antibodies. The overall prevalence of HTLV-1/2 was 1.67 per 100,000 (1/59,929).
No changes were found in the results of the indeterminate and positive cases after the follow-up test in three months, while one indeterminate case from Hebei tested negative in the second follow-up test (Fig. 2).
The demographic characteristics showed that the blood donor with HTLV-1 infection in the study was a 32-year-old first-time female donor from the Fujian province who belonged to the SHE ethnicity minority and had a high school degree. She was unmarried and had three sexual partners with unprotected sex. In addition, she once pierced her ear, received acupuncture therapy, and had endoscopy twice. Three blood donors with indeterminate results belonged to the HAN ethnicity. Most of the indeterminate cases were unmarried workers and first-time donors with associate degrees (Table 3).
The L2400 and INNO-LIA HTLV I/II score among blood donations varied; the S/CO values of 32 reactive blood plasma samples, ranging from 1.0 to 5.0, comprised of 84.4% (27/32) of the samples, only 15.6% (5/32) samples had an S/CO value > 5.0. Seven samples had lines upon confirmation (gag p19 I/II, gag p24 I/II, env gp46 I/II, env gp21 I/II). Of these, 3 donations with a single gp46 I/II band were identified as negative for HTLV antibodies, while 3 samples with single gp21 I/II were classified as indeterminate for antibodies. Only one donation had the 4 confirmation lines and was confirmed as HTLV-1 positive due to the 2 bands of discrimination (p19 I and gp46 I).