Introduction
Blood transfusion is an essential therapeutic procedure for obstetric hemorrhage, trauma, surgery, hematological disorders, and chronic diseases. More than 118 million donations are collected annually worldwide, with marked disparities between high-income and low- and middle-income countries.1
In sub-Saharan Africa, transfusion safety remains a challenge due to low proportion of regular voluntary donors, inadequate infrastructure, and burden of transfusion-transmissible infections (TTIs) including HIV, HBV, HCV, and syphilis.2–4 Recent meta-analyses and systematic reviews report prevalence ranges 1–7% for HIV, 4–12% for HBV, 1–5% for HCV, 2–8% for syphilis across region with similar ranges in recent updates.3,5–9 Viral hepatitis causes ~1.3 million deaths annually from cirrhosis and hepatocellular carcinoma.4
WHO recommends systematic screening of every donation for HIV, HBV, HCV, syphilis using validated assays under quality assurance.4 In resource-limited settings, serologic rapid diagnostic tests (RDTs) are widely used due to cost, infrastructure, and turnaround time, whereas universal molecular screening (nucleic acid testing, NAT) further reduces residual risk but is not universally available due to cost and technical requirements. Understanding performance and limitations of serologic screening in such settings is therefore relevant.
In Chad, transfusion safety faces inadequate national coverage and high TTI burden.10 National HIV prevalence declined from 1.6% (DHS 2014–2015) to ~1.2% Spectrum 2023.11 Syphilis prevalence was 2.5% among donors at Abéché University Hospital12 and 2.65% among 24,587 donors at National Blood Transfusion Center in N’Djamena.13 Data on HBV and HCV are limited.
To our knowledge, no study has simultaneously assessed screening markers for HIV, HBV, HCV, and syphilis among donors at Provincial Hospital of Sarh, capital of Moyen-Chari Province (9°09’N 18°23’E), a 120-bed referral facility serving a rapidly growing population (81,400 in 1997 to 133,757 in 2019).14–16 Local data are needed. It is important to distinguish donor screening-marker reactivity (observed in a selected population dominated by family/replacement donors) from confirmed infection prevalence in general population.
The primary objective of this study was to estimate the prevalence of reactive screening markers for HIV, HBV, HCV, and syphilis among blood donors at Sarh Provincial Hospital during September 18 to November 18, 2023, with 95% confidence intervals. Secondary objective was to describe distribution by demographic characteristics. The term “associated factors” is not used as inferential analysis is not performed; associations are presented descriptively.
Materials and Methods
Study Setting
Study conducted in Sarh, capital of Moyen-Chari Province and Bahr-Kôh Department, Chad (18°23’E, 9°09’N). Sarh Provincial Hospital is a 120-bed referral facility comprising Internal Medicine, Obstetrics and Gynecology, Pediatrics, Emergency, Surgery, and a blood bank responsible for collection, screening, and provision of blood products.16 Main economic activities agriculture, livestock, trade, industry.15
Study Design and Period
Retrospective cross-sectional study using routinely collected data from blood bank registers of SPH. Study period September 18 to November 18, 2023 (2 months). This short period is substantial for descriptive estimation (n=2,841) but cannot establish annual prevalence, temporal trends, or seasonal variation; conclusions restricted to study period.
Study Population and Sampling
Study population: individuals presenting for blood donation at SPH during study period and registered in blood bank records. Consecutive sampling: all eligible donors recorded during period, voluntary and family/replacement donors, considered.
Eligibility Criteria
Inclusion: aged 18–60 years per national eligibility, weight ≥60 kg, considered eligible after pre-donation interview and clinical assessment with no contraindication, adequate hemoglobin, blood sample suitable for serological testing for HIV, HBV, HCV, syphilis, registered at SPH during period. Exclusion: records not meeting eligibility, incomplete/missing demographic or serological results, unusable/uninterpretable serological results, samples unsuitable due to inadequate volume, hemolysis, clotting, or pre-analytical problems. Participant flow: 2,868 records initially identified, 27 excluded (12 incomplete demographic, 10 missing serology, 5 unsuitable sample), final analytical sample 2,841.
No duplicate/repeat donors identified via unique ID check. Missing data proportion 0.94% handled by exclusion.
Serological Testing for Transfusion-Transmissible Infections
Screening performed using RDTs per blood bank procedures and WHO recommendations for resource-limited settings.17 Specimen: venous whole blood collected, serum/plasma used as per manufacturer. Assays: HIV screened with Determine HIV-1/2 (Abbott Laboratories, USA) detects antibodies against HIV-1/2;18 HBV screened by HBsAg detection with HBsAg Rapid Test Cassette Serum/Plasma (Hangzhou AllTest Biotech, China);19 HCV screened by anti-HCV antibodies with HCV Ab Test Cassette Serum/Plasma (Qingdao Hightop Biotech, China);20 Syphilis screened with Syphilis Rapid Test Strip Whole Blood/Serum/Plasma (Rapid Labs Ltd., UK), treponemal assay.21 Testing algorithm: single RDT per marker per hospital protocol, no repeat testing algorithm or confirmatory testing available during study period due to resource limitations. Quality control: daily internal control per manufacturer, external QA quarterly via National Blood Transfusion Program.
Results recorded as reactive/non-reactive per manufacturer interpretation. In absence of confirmatory testing, reactive results considered screening reactive, not interpreted as laboratory-confirmed infections. Anti-HCV reactivity does not establish active HCV infection.
Treponemal syphilis reactivity may persist after treatment.
Data Collection
Two registers reviewed: one sociodemographic/donation-related (age, sex, marital status, occupation, donation type, ABO/Rh), second screening results (HIV, HBV, HCV, syphilis). Each donor identified by unique ID enabling linkage without directly identifying information. Data extracted independently by two trained staff, cross-checked via ID, recorded on standardized form, entered into Microsoft Excel 2016, validated.
Donors informed before collection that samples would be screened for TTIs, procedure benefits/risks, confidentiality. Verbal informed consent obtained as part of routine donation process for screening, confidential result communication, and referral. For present retrospective study, only routinely collected recorded data extracted, no directly identifying information collected or reported.
Data Analysis
Data entered Excel 2016, imported into IBM SPSS Statistics v26.0 (IBM Corp., Armonk, NY, USA). Outcome clearly defined as reactive vs non-reactive screening marker per assay. Prevalence calculated as reactive n/total tested×100, 95% CI calculated by Wilson score method (exact Clopper-Pearson for zero events).
Categorical variables summarized as n (%). Exact numerators and denominators reported. Chi-square test and Fisher exact test (when expected <5) compared distributions by age and sex, p<0.05 considered significant, trend analysis by chi-square for trend.
Distinction maintained between descriptive observations and inferential conclusions. Associated factors terminology avoided as multivariable inferential analysis not performed; objective is descriptive prevalence estimation. Multiple-marker reactivity reconstructed using unique donors rather than sum of assay-level reactive results.
Post-hoc sample size: single population proportion formula, expected HBV 9.68% from present data, precision 2%, confidence 95%, required 841, our 2,841 exceeds. Mean age calculated 30.2±9.1 years.
Ethical Considerations
Retrospective secondary use of routine donor registers. Approval obtained from Sarh Provincial Hospital Ethics Committee and Medical Director (Ref: N°1100/PMC/DPSPMC/HPDOBS/SGH/SP/SG/2023, dated 12 September 2023). Written waiver of informed consent for retrospective record review granted, as verbal consent was obtained at time of donation for screening, confidential result communication, and referral as part of routine process.
No additional consent required for this retrospective analysis. No directly identifying information extracted or reported. Confidentiality protected via unique ID.
Results communicated individually/confidentially to donors per blood bank procedures and referred to infectious disease clinic for counseling and confirmatory testing where available, but confirmatory results not captured in blood bank registers. No changes to ethics declarations without prior agreement with Editorial Department.
Results
Participant Selection: Figure 1 shows flow. Of 2,868 records initially identified between September 18 and November 18, 2023, 27 were excluded (12 incomplete demographic, 10 missing serological results, 5 unsuitable samples). Final analytical sample 2,841 blood donors included (Figure 1).
Figure 1Participant selection flow diagram.A flowchart of blood donor record selection, exclusions and final analysis count.Notes: Of 2,868 records identified, 27 were excluded (12 with incomplete demographic data, 10 with missing serology, and 5 with unsuitable samples); 2,841 donors were included in the final analysis. No duplicate/repeat donors were identified by unique identification number.
Demographic and Socioeconomic Characteristics (Table 1): Total N=2,841. Age groups: 18–28 years 1,275 (44.88%, men 975/34.32% women 300/10.56%), 29–39 years 1,008 (35.47%), 40–50 years 482 (16.97%), 51–60 years 76 (2.67%). Men 2,173 (76.49%), women 668 (23.51%), ratio 3.25:1, mean age 30.2±9.1 years.
Donor type: family/replacement 2,778 (97.75%), voluntary non-remunerated 63 (2.22%), missing 0.03%. Occupation: Employed 1,822 (64.13%, including farmers/livestock breeders 636/22.39%, trade 312/10.98%, civil servants 248/8.73%), Unemployed 1,019 (35.87%). Marital status: Married 2,077 (73.11%), Single 728 (25.62%), Widowed 19 (0.67%), Divorced 18 (0.63%).
Total N=2,841 consistent across variables after final cleaned dataset audit; previous discrepancy 2,173/668 vs 2,174/667 corrected to 2,173/668.Table 1Demographic and Socioeconomic Characteristics of Blood DonorsVariablesModalitiesTotal SampleMenMenWomenWomennn%n%Age groups[18–28]127597534.3230010.56[29–39]100877127.132378.34[40–50]48236912.991133.98[51–60]76582.04180.63Total2841217376.4966823.51OccupationEmployed1822139449.0642815.06Unemployed101977927.422408.45Total2841217376.4966823.51Marital statusMarried2077158855.8948917.21Single72855719.611716.02Widowed19150.5340.14Divorced17130.4640.14Total2841217376.4966823.51Donor typeFamily/replacement2778212674.8465222.95Voluntary63471.65160.56Notes: N=total sample size (2841 blood donors). n=absolute frequency (number of donors) in each modality. %=relative frequency calculated as n/N×100. Men 2173 (76.49%) Women 668 (23.51%). Mean age 30.2±9.1 y.
Family/replacement 2778 (97.77%) Voluntary 63 (2.22%).
Prevalence of Reactive Screening Markers (Table 2): HBV (HBsAg reactive) 275 (9.68%, 95% CI 8.64–10.83), Syphilis (treponemal reactive) 177 (6.23%, 5.39–7.18), HCV (anti-HCV reactive) 104 (3.66%, 3.03–4.42), HIV (reactive) 95 (3.34%, 2.74–4.07). Total N=2,841 for each marker. HBV shows highest reactivity among four markers.
Unique donors with ≥1 reactive marker 584 (20.56%, 95% CI 19.11–22.09).Table 2Prevalence of Reactive Screening Markers for Transfusion-Transmissible InfectionsMarkersNon-ReactiveNon-ReactiveReactiveReactiveTotaln%n%N (%)HBV (HBsAg)256690.322759.68 [8.64–10.83]2841 (100)Syphilis (treponemal)266493.771776.23 [5.39–7.18]2841 (100)HCV (anti-HCV)273796.341043.66 [3.03–4.42]2841 (100)HIV (HIV-1/2 Ab)274696.66953.34 [2.74–4.07]2841 (100)Notes: N=total sample size 2841. n=absolute frequency. %=prevalence n/N×100 with 95% Wilson CI in brackets for reactive. Assays: Determine HIV-1/2 Abbott, HBsAg Rapid AllTest, HCV Ab Hightop, Syphilis Rapid treponemal Rapid Labs. Reactive/Non-reactive per manufacturer.
No confirmatory testing; screening-marker reactivity only.
Distribution by Age, Occupation, Marital Status (Table 3 and Table 4): For age groups and marital status, percentages are row percentages (prevalence within modality). For occupation, percentages are column percentages (distribution within serostatus) explicitly defined in footnotes. No statistically significant age trend for HBV (chi-square for trend p=0.48) or HCV (p=0.20).
HIV reactivity by age: 18–28 46/1,275=3.61%, 29–39 31/1,008=3.07%, 40–50 15/482=3.11%, 51–60 3/76=3.95%, p=0.88. Syphilis 18–28 86/1,275=6.75%, 29–39 61/1,008=6.05%, 40–50 27/482=5.60%, 51–60 3/76=3.95%, p=0.72. HBV 18–28,118/1,275=9.25%, 29–39,101/1,008=10.02%, 40–50 47/482=9.75%, 51–60 9/76=11.84%, p=0.48.
HCV 18–28 42/1,275=3.29%, 29–39 37/1,008=3.67%, 40–50 21/482=4.36%, 51–60 4/76=5.26%, p=0.20. Occupation: Employed HIV reactive 60/1,822=3.29% vs Unemployed 35/1,019=3.43% p=0.84; HBV Employed 182/1,822=9.99% vs Unemployed 93/1,019=9.13% p=0.45. Marital status distributions similar, no significant differences after formal testing.Table 3Distribution of Reactive Markers for HIV and Syphilis by Age, Occupation and Marital StatusVariablesModalitiesHIVHIVHIVHIVSyphilisSyphilisSyphilisSyphilisNon-reactiveNon-reactiveReactiveReactiveNon-reactiveNon-reactiveReactiveReactiven%n%n%n%Age groups[18–28]122996.39463.61118993.25866.75[29–39]97796.93313.0794793.95616.05[40–50]46796.89153.1145594.40275.60[51–60]7396.0533.957396.0533.95OccupationEmployed176264.16*6063.16*170664.04*11665.54*Unemployed98435.84*3536.84*95835.96*6134.46*Marital statusMarried200696.63703.37194693.741306.26Single70496.70243.3068393.82456.18Widowed1894.7415.261894.7415.26Divorced18100.0000.001794.4415.56Notes: N=2841 n=absolute frequency.
Age/marital %=row percentage (prevalence within modality). Occupation *=column percentage (distribution within serostatus). HIV Non-reactive 2746 Reactive 95; Syphilis Non-reactive 2664 Reactive 177.
No significant age trend HIV p=0.88 Syphilis p=0.72.Table 4Distribution of Reactive Markers for HBV and HCVVariablesModalitiesHBV (HBsAg)HBV (HBsAg)HBV (HBsAg)HBV (HBsAg)HCV (anti-HCV)HCV (anti-HCV)HCV (anti-HCV)HCV (anti-HCV)Non-reactiveNon-reactiveReactiveReactiveNon-reactiveNon-reactiveReactiveReactiven%n%n%n%Age groups[18–28]115790.751189.25123396.71423.29[29–39]90789.9810110.0297196.33373.67[40–50]43590.25479.7546195.64214.36[51–60]6788.16911.847294.7445.26OccupationEmployed164063.92*18266.18*175063.94*7269.23*Unemployed92636.08*9333.82*98736.06*3230.77*Marital statusMarried187690.372009.63200496.53723.47Single65890.38709.6269996.02293.98Widowed1789.47210.5319100.0000.00Divorced1583.33316.671583.33316.67Notes: Row % for age/marital, *column % for occupation. HBV Non-reactive 2566 Reactive 275; HCV Non-reactive 2737 Reactive 104. No significant age trend HBV p=0.48 HCV p=0.20.
Distribution by Sex (Table 5): Men n=2,173 Women n=668 harmonized. HBV Men 215/2,173=9.90% Women 60/668=8.98% p=0.49. Syphilis Men 140/2,173=6.44% Women 37/668=5.54% p=0.40.
HCV Men 76/2,173=3.50% Women 28/668=4.19% p=0.40. HIV Men 72/2,173=3.31% Women 23/668=3.44% p=0.87. All sex differences not statistically significant.
Previous calculation errors corrected: Female HIV previously reported 23/667=3.34% corrected to 23/668=3.44%, Female HBV 607/667=91% corrected to 607/668=90.87% non-reactive etc, all percentages regenerated directly from cleaned dataset.Table 5Distribution of Reactive Markers by SexMarkersMen (n=2173)Men (n=2173)Men (n=2173)Men (n=2173)Women (n=668)Women (n=668)Women (n=668)Women (n=668)Non-reactiveNon-reactiveReactiveReactiveNon-reactiveNon-reactiveReactiveReactiven%n%n%n%HBV195890.102159.9060891.02608.98Syphilis203393.561406.4463194.46375.54HCV209796.50763.5064095.81284.19HIV210196.69723.3164596.56233.44Notes: Men 2173 Women 668 harmonized consistent. n=absolute frequency %=row % within sex. No significant sex differences all p>0.40. Female HIV 23/668=3.44% corrected (previously 3.34%).
Multiple-Marker Reactivity (Table 6): Of 2,841 donors, 584 had ≥1 reactive marker (20.56%). Among them, 64 had multiple-marker reactivity (2.25% of all donors, 10.96% of reactive donors, 64/584). Assay-level reactive events sum 651 (HBV 275+Syphilis 177+HCV 104+HIV 95).
Most frequent combination HBV+Syphilis 15 (0.53% of all donors, 2.30% of assay-level events, 2.57% of reactive donors). HIV+Syphilis 14 (0.49%), HCV+Syphilis 12 (0.42%), HCV+HBV 11 (0.39%), HIV+HBV 6 (0.21%), HIV+HCV 3 (0.11%), triple combinations each 1 (0.04%). No quadruple reactivity.
Term “coinfection” replaced with “multiple-marker reactivity” as confirmatory testing not performed. Previous denominator 651 represented sum of assay-level reactive results, not unique donors; now clarified with both denominators: % among total donors (N=2,841) and % among reactive donors (n=584) and % among assay-level events (n=651) for transparency.Table 6Prevalence of Multiple-Marker Reactivity Among Blood DonorsMultiple-Marker Reactivityn% N=2841% n=584 Reactive Donors% n=651 Assay EventsHBV + Syphilis150.532.572.30HIV + Syphilis140.492.402.15HCV + Syphilis120.422.051.84HCV + HBV110.391.881.69HIV + HBV60.211.030.92HIV + HCV30.110.510.46HIV + HCV + Syphilis10.040.170.15HIV + HBV + Syphilis10.040.170.15HBV + HCV + Syphilis10.040.170.15HIV + HBV + HCV00.000.000.00HIV + HBV + HCV + Syphilis00.000.000.00Total multiple-marker642.2510.969.83Total ≥1 reactive58420.56100.00-Notes: N=total donors 2841 n=absolute frequency %=prevalence. Unique donors ≥1 reactive 584 (20.56%).
Multiple-marker 64 (2.25% all donors, 10.96% reactive donors). Assay-level events sum 651. Term coinfection replaced with multiple-marker reactivity as no confirmatory testing.
No quadruple reactivity.
Discussion
This study provides recent blood-donor screening data from Sarh Provincial Hospital, an apparently understudied setting in Chad, using a relatively large donor population (n=2,841) over 2 months. The principal contribution is geographical and contextual.
The observed reactive screening markers: HBV (HBsAg) 9.68% falls within SSA range 4–12% reported in recent meta-analysis3,5 and is higher than 2.5% previously reported at Abéché University Hospital12 but similar to ~10.1% reported at National Blood Transfusion Center N’Djamena.13 Our finding suggests persistent high HBV burden in this region. Future trend may remain high without expanded vaccination and voluntary donor promotion.
HCV (anti-HCV) 3.66% falls within SSA range 1–5%.3,5 Anti-HCV antibody reactivity does not establish active HCV infection; it may represent past infection, current infection, or false reactivity, requiring confirmatory RNA testing.
HIV screening reactivity 3.34% (95% CI 2.74–4.07) is substantially higher than national estimate 1.2% Spectrum 202311 and 1.6% DHS 2014–2015, but higher reactivity among blood donors dominated by family/replacement donors is expected due to selection bias, higher risk in replacement donors, and assay characteristics (Determine HIV-1/2 screening without confirmatory). Among voluntary non-remunerated donors, HIV reactivity 0/63 (0%, exact 95% CI 0–5.65) indicates that zero events in this small subgroup does not establish absence of reactivity; upper bound 5.65%. This distinction is important.
Syphilis treponemal screening reactivity 6.23% (5.39–7.18) exceeds 2.5% reported at Abéché12 and 2.65% among 24,587 donors at N’Djamena.13 Differences may be due to assay methodology (treponemal vs non-treponemal), donor selection (family/replacement predominance), geography, and persistent treponemal reactivity after treatment. Treponemal assays remain reactive for life even after successful treatment, thus reactive result does not necessarily indicate active syphilis.
Age and sex differences: Data do not support statistically significant age trend for HBV (p=0.48) or HCV (p=0.20), nor significant sex differences (all p>0.40). Age and sex are presented descriptively. Claims that HBV and HCV reactivity were higher among family/replacement donors cannot be evaluated because corresponding results were not presented stratified by donor type in initial submission; we now provide: family/replacement reactive markers 574/2,778=20.66% vs voluntary 10/63=15.87% p=0.36, no significant difference.
No behavioral data were collected, therefore behavioral explanations such as “high-risk sexual behaviours”, “unprotected sexual practices”, and “shared risk factors” are unsupported and removed.
Multiple-marker reactivity: 64 donors (2.25% of all donors) showed reactivity for more than one marker. Under independence, expected HBV+Syphilis prevalence = 9.68%*6.23% = 0.60%, observed 0.53% approximately expected. HCV+Syphilis expected 0.23% observed 0.42% appears more frequent descriptively, but this does not establish causal or behavioral association and may be due to chance, assay cross-reactivity, or unmeasured confounding.
Interpretation remains speculative without confirmatory testing and behavioral data.
Screening-marker reactivity is not equivalent to confirmed infection prevalence in general population nor to residual transfusion-transmission risk. WHO recommends systematic screening for HIV, HBV, HCV, syphilis using validated assays under quality assurance.4 In resource-limited settings like Chad, RDTs are used due to cost, infrastructure, and turnaround time, while universal molecular NAT screening further reduces residual risk but is not universally available. Our study relied on RDTs without confirmatory testing, a limitation inherent to setting.
Limitations: Single-hospital, 2-month period, cannot establish annual prevalence, temporal trends, or seasonal variation; conclusions restricted to study facility and period. Rapid assays without confirmatory serological or molecular testing; reactive results are screening reactivity, not confirmed infections. No data on duplicate donors beyond unique ID check, no behavioral data, no ABO/Rh analysis presented.
Referral for confirmatory testing and counseling performed but confirmatory results not captured in registers. Despite limitations, sample size substantial for descriptive estimation during period.
Comparison with broader region/continent: SSA donor data show HBV 4–12%, HIV 1–7%, HCV 1–5%, syphilis 2–8%;3,5 our HBV and syphilis at upper range, HIV and HCV within range, consistent with resource-limited settings with high replacement donor proportion.
Conclusion
In this single-hospital, 2-month retrospective study at Sarh Provincial Hospital based on rapid diagnostic tests without confirmatory serological or molecular testing, reactive screening markers were observed in 20.56% of donors, with HBV (HBsAg) 9.68% and syphilis (treponemal) 6.23% being most frequent. The findings are based on screening-marker reactivity, not laboratory-confirmed infections, and should be interpreted in accordance with screening methods used and absence of confirmatory testing. They cannot be considered representative of southern Chad, all donors at the hospital over time, or the general population.
Strengthening recruitment and retention of voluntary non-remunerated blood donors, quality assurance, access to confirmatory testing and referral for counseling where available, and epidemiological surveillance are important strategies for improving blood transfusion safety in Chad.