Demographic details of the blood donors
In the present study, data from a total of 31,931 blood donors including 31,598 (98.96%) males and 333 (1.04%) females from June 2015 to December 2023 were screened. Of these, 31,338 (98.14%) were replacement donors, while the remaining 593 (1.86%) were voluntary donors. The percentage of female donors was significantly lower across all studied groups. The mean age, weight, and hemoglobin (Hb) level of the blood donors were 31.97 ± 6.37 years, 69.56 ± 6.88 kg, and 13.6 ± 0.85 g%, respectively, with no significant differences observed between replacement and voluntary donors. The majority of the blood donors (92.47%) belonged to the 18–40 years age group, with the highest proportion (31.71%) in the 26–30 years age group, compared to only 7.54% in the 41–55 years age group. Among replacement donors, 64% were from rural areas, whereas 68.13% of voluntary donors were from urban areas. In terms of religion, almost 75% of donors were from the Hindu community, followed by Islamic (21.13%), Christian (1.51%), Sikh (1.32%), and Buddhist (0.99%) communities. The most common blood group among donors was O-Positive (37.03%), followed by B-Positive (30.23%), A-Positive (22.85%), and AB-Positive (7.05%). Only 2.84% of donors were Rhesus-negative (Table 1).
Demographic details of TTI-reactive donors
Out of a total of 31,931 blood donors, 949 (2.97%) tested positive for at least one transfusion-transmissible pathogen. The positivity rate was relatively higher among males than females (2.97% vs. 0.32%), in the 18–40 years age group compared to other age groups (2.52% vs. 0.44%), among rural compared to urban inhabitants (1.84% vs. 1.14%), among Hindus compared to other religions (2.16% vs. 0.8%), and among Rhesus-positive donors compared to Rhesus-negative donors (2.88% vs. 0.09%). However, these differences in occurrence were not statistically significant. The blood group with the highest positivity rate was O-Positive (1.08%), followed by B-Positive (0.88%), A-Positive (0.68%), and AB-Positive (0.24%). There were no significant differences in the mean age, weight, or Hb levels between replacement and voluntary blood donors (Table 2).
Prevalence of TTIs
The overall prevalence of TTIs in the study was observed to be 3.1%. Among the TTIs, HCV (1.14%) had the highest prevalence, followed by syphilis (1.0%), HBV (0.54%), HIV (0.41%), and malaria (0.01%). A total of 39 donors (0.12%) tested positive for multiple (mixed) TTIs. The multiple TTI positivity rate was higher among Rhesus-negative donors (0.22%) compared to Rhesus-positive donors (0.12%), although the difference was statistically insignificant (p = 0.86). The highest prevalence of TTIs was observed in the year 2021 (4.18%), followed by 2023 (4.15%), 2018 (3.17%), 2022 (2.98%), 2020 (2.68%), 2019 (2.37%), 2016 (2.29%), 2017 (2.12%), and 2015 (1.54%). In terms of individual TTIs, the highest prevalence of HBV (0.66%) and HCV (1.68%) was observed in 2023, HIV (0.69%) in 2018, and syphilis (1.58%) in 2021 (Table 3).
Prevalence of TTIs among studied blood groups
Out of the total 989 TTI-positive cases (including the mixed infections), A, AB, B, O, Rhesus-positive, and Rhesus-negative blood donors were 233 (3.08%), 84 (3.57%), 298 (3.02%), 374 (3.08%), 958 (3.09%), and 31 (3.41%), respectively. The overall TTI reactivity was observed to be higher among Rhesus-negative blood donors compared to Rhesus-positive donors (3.41% vs. 3.09%), particularly in cases of syphilis infection (1.87% vs. 0.97%). Of the 173 (0.54%) HBV-positive donors, the percentages of A, AB, B, O, Rhesus-positive, and Rhesus-negative donors were 38 (0.5%), 10 (0.43%), 49 (0.5%), 76 (0.63%), 169 (0.54%), and 4 (0.44%), respectively. A total of 364 (1.14%) blood donors were tested positive for HCV, with 84 (1.11%) A, 27 (1.15%) AB, 103 (1.04%) B, 150 (1.24%) O, 356 (1.15%) Rhesus-positive, and 8 (0.88%) Rhesus-negative donors. The percentages of A, AB, B, O, Rhesus-positive, and Rhesus-negative blood group among HIV-positive donors were 33 (0.44%), 15 (0.64%), 42 (0.43%), 41 (0.34%), 129 (0.42%), and 2 (0.22%), respectively. Only 2 (0.02%) blood donors of the O Rhesus-positive blood group were tested positive for malaria. Of the total 319 (1%) syphilis-positive donors, the proportions of A, AB, B, O, Rhesus-positive, and Rhesus-negative donors were 78 (1.03%), 32 (1.36%), 104 (1.05%), 105 (0.86%), 302 (0.97%), and 17 (1.87%), respectively. The TTI positivity rate was higher among donors with the AB blood group (3.57%) compared to others. Regarding the prevalence of individual TTIs, syphilis showed the highest prevalence rate of 1.36%, primarily involving AB group blood donors, followed by HCV infection (1.24%), which mostly affected O group donors. Donors with the O blood group demonstrated a somewhat higher prevalence (0.16%) of multiple infections compared to other blood groups (Table 3).
Trends of TTIs
The results of the present study revealed a consistent increase in the cumulative frequency of overall TTI positivity from 2015 to 2023, with the exception of 2022, when a slight decline in frequency was observed. Notably, the prevalence of TTIs showed a general upward trend, with significant increases in 2016, 2018, and 2021.
In particular, HCV prevalence exhibited a clear rise, increasing from 0.51% in 2015 to 1.68% in 2023, despite slight decreases in 2016 (0.46%) and 2022 (1.01%). On the other hand, HBV prevalence remained relatively stable throughout the study period, while other TTIs did not follow a discernible trend (Fig. 1).
Graphical representation of the trend of TTI prevalence.
A total of 173 (0.54%) blood donors tested positive for HBV. Among them, the distribution by blood group was as follows: A (38, 0.5%), AB (10, 0.43%), B (49, 0.5%), O (76, 0.63%), Rhesus-positive (169, 0.54%), and Rhesus-negative (4, 0.44%). For HCV, 364 (1.14%) blood donors were positive. Their distribution was: A (84, 1.11%), AB (27, 1.15%), B (103, 1.04%), O (150, 1.24%), Rhesus-positive (356, 1.15%), and Rhesus-negative (8, 0.88%). A total of 131 (0.41%) blood donors were positive for HIV-I/II, distributed as follows: A (33, 0.44%), AB (15, 0.64%), B (42, 0.43%), O (41, 0.34%), Rhesus-positive (129, 0.42%), and Rhesus-negative (2, 0.22%). Only 2 blood donors with the O Rhesus-positive blood group tested positive for malaria. A total of 319 (1.0%) blood donors were positive for syphilis. Their distribution was: A (78, 1.03%), AB (32, 1.36%), B (104, 1.05%), O (105, 0.86%), Rhesus-positive (302, 0.97%), and Rhesus-negative (17, 1.87%) (Table 3).
Association of individual TTI with different blood groups
The relative percentages of HBV (43.93% vs. 5.78%), HCV (41.21% vs. 7.42%), HIV (31.3% vs. 11.45%), and syphilis (32.92% vs. 10.03%) positivity were significantly higher in donors without any ABO antigens (O group) compared to donors with both A and B antigens (AB group). A statistically significant association (p < 0.05) was observed between donors lacking ABO antigens and those possessing both A and B antigens across all TTI-positive cases. The highest positivity rates for TTIs were observed in donors without any antigens, except for HIV, where donors with the B antigen exhibited the highest positivity rate (32.06%), slightly surpassing those without any antigens (31.3%). However, this difference was minimal. In Rhesus negative blood donors, percentage of HBV, HCV and HIV positivity was slightly lower (2.31%, 2.2%, 1.53%, respectively) than the HBV, HCV and HIV negative donors (2.85% in all). Whereas, in Rhesus positive donors, percentage of HBV, HCV and HIV positivity was higher (97.69%, 97.8%, 98.47%, respectively) than the HBV, HCV and HIV negative donors (97.15% in all), but the association was not statistically significant. For syphilis, a divergent pattern was observed between Rhesus-negative and Rhesus-positive blood donors among both syphilis positive and negative cases, but this association was also not statistically significant (p > 0.05). The magnitude of TTIs in Rhesus-negative donors (2.84%) was lower compared to Rhesus-positive donors (97.16%) (Table S1, Supplementary File).
Multiple (Mixed) TTI positivity
Among the 39 donors who tested positive for multiple TTIs, all were replacement donors (Table S2, Supplementary File).
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HBV and HCV dual positivity: 12 donors (0.038%) were positive, 10 (0.031%) of whom belonged to the O Rhesus-positive blood group.
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HBV and syphilis dual positivity: 2 donors (0.006%) were positive: one with A Rhesus-positive and one with O Rhesus-positive blood groups.
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HCV and HIV dual positivity: 6 donors (0.019%) were positive: 1 with A Rh-positive, 3 with B Rh-positive, and 2 with O Rh-positive blood groups.
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HCV and syphilis dual positivity: 2 donors (0.006%) were positive: one with AB-positive and one with B Rhesus-negative blood groups.
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HIV and syphilis dual positivity: 16 donors (0.05%) were positive: 5 with A-positive, 2 with AB-positive, 3 with B-positive, and 6 with O-positive blood groups.
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Triple TTI positivity (HCV, HIV, and syphilis): Only 1 donor (0.003%) was found to have triple infections, belonging to the B-positive blood group.
TTI positivity rate by demographic variables
When analyzing the frequency of individual TTIs by various demographic criteria, significant associations were observed with age group (p < 0.0001) and locality (p = 0.0008). Other demographic variables such as gender, religion and donor type failed to demonstrate any significant associations with the TTI positivity rate. Out of a total of 333 female donors, only one donor, having blood group “O” Rhesus-positive, tested positive for TTI (syphilis).
Age group
The prevalence of TTIs showed a decreasing trend with increasing age until 40 years, followed by a rise among middle-aged donors, with a sudden peak in the 46–50-year age group (14.63%). This age group exhibited particularly high positivity rates for HBV (2.09%) and syphilis (9.85%) compared to other age groups. Conversely, HCV (3.07%) and HIV (0.8%) were most prevalent in the 18–25-year age group. The 36–40-year age group demonstrated the lowest TTI prevalence (1.54%), which was consistent across all TTIs: HBV (0.39%), HCV (0.36%), HIV (0.14%), and syphilis (0.65%).
Locality
Except for syphilis, other TTIs were more prevalent among urban blood donors compared to rural donors (3.23% vs. 3.02%).
Religious communities
Donors from the Islamic community had the highest TTI positivity rate (3.35%), followed by Buddhist (3.16%), Sikh (3.09%), Hindu (3.03%), and Christian donors (2.9%).
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HBV prevalence was highest among Christian donors (1.04%).
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HCV prevalence was highest among Sikh donors (1.43%).
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HIV (0.52%) and syphilis (1.14%) were most prevalent among Islamic donors.
Donation type
The prevalence of TTIs was higher, though not statistically significant, among replacement donors (3.14%) than voluntary donors (0.84%). All five TTIs were more prevalent in replacement donors compared to voluntary donors (Table 4).
Multivariate analysis (Table S3, Supplementary File) revealed a statistically significant association between the overall prevalence of TTIs and both age (p < 0.0001) and locality (p = 0.01).