This was a cross-sectional, descriptive and analytical study with prospective data collection, conducted from March 1 to November 30, 2025 (nine months) at the RFTC of Brazzaville. The RFTC is the sole public hemodialysis center in Brazzaville, with 30 dialysis stations.

The study was approved by the Ethics Committee of the Faculty of Health Sciences, Marien Ngouabi University (approval no. 25-082 UMNG/FSSA/CAB-DOY-VD) and authorized by the RFTC Director. It was conducted in accordance with the Declaration of Helsinki and good clinical practice guidelines. Written informed consent was obtained from each participant prior to any study procedure. All data were anonymized by numerical coding. No financial compensation was provided; biological investigations were offered free of charge. The authors declare no conflicts of interest.

All chronic hemodialysis patients receiving care at the RFTC during the study period were eligible. Inclusion criteria were: I) age ≥ 18 years; II) chronic hemodialysis for at least three months; III) written informed consent. Exclusion criteria were: hemodialysis for acute kidney injury and refusal to participate.

The minimum sample size was calculated using the Schwartz formula: n = Z²·p·(1 − p)/d², with Z = 1.96 (5% significance level), an estimated prevalence p = 23% (pooled African prevalence, Adane and Getawa [4]), and a precision d = 7.5%. This formula yielded a minimum of 121 patients, increased to 160 after applying a finite population correction factor and a 30% allowance for potential incomplete data. The final included sample of 125 patients falls slightly below this target, which constitutes a study limitation (see Section 4.5).

For each enrolled patient, sociodemographic data (sex, age, nationality, educational level, marital status, religion, residence), clinical data (comorbidities, lifestyle, history of blood transfusion, tattooing, piercing), and therapeutic data (hemodialysis duration, type of vascular access, session modalities) were collected using a standardized questionnaire administered during an individual interview. Glomerular filtration rate (GFR) and CKD stage were recorded.

2.5.1. Rapid Diagnostic Test (RDT)

A qualitative immunochromatographic RDT was performed at the bedside to detect anti-HCV antibodies (SD Bioline HCV kit, Standard Diagnostics Inc., Republic of Korea; reference: 06FK60; specimen: 10 µL serum or venous whole blood collected in a dry tube, placed in the sample well with 3 drops of buffer; visual reading at 15 minutes). A positive result required the appearance of a colored band in both the control (C) and test (T) zones. Internal positive and negative controls provided with the kit were systematically verified before each test series. Each reagent lot was subject to documented compliance verification by the responsible biologist.

2.5.2. ELISA Confirmation

All RDT-positive samples were systematically confirmed by sandwich ELISA (Sirio S analyzer, Radim S.p.A., Italy; anti-HCV antibody ELISA kit, 3A Laboratory, Brazzaville; specimen: 5 mL venous blood in a dry tube). Samples were transported in an isothermal bag (2˚C - 8˚C) and stored at −80˚C until analysis. After 30 minutes of coagulation at room temperature, tubes were centrifuged at 2500 rpm for 5 - 10 minutes. Optical density (OD) was measured at 450 nm; positivity threshold = mean negative control OD + 0.15. A sample was considered positive if OD ≥ positivity threshold. Calibrated positive and negative controls (kit-provided) were included in each ELISA plate to validate each run.

Data were entered and cleaned using Microsoft Excel 2021. Statistical analysis was performed with SPSS version 25.0 (IBM Corp., Armonk, NY, USA). Normality of distributions was assessed using the Shapiro-Wilk test. Quantitative variables were expressed as mean ± standard deviation (SD). Qualitative variables were expressed as frequency and percentage. Between-group comparisons used Pearson’s chi-squared test (or Fisher’s exact test when expected cell frequency < 5). Crude odds ratios (ORs) with 95% confidence intervals (95% CI) were calculated in univariate analysis. The significance threshold was set at 5%. Given the small number of positive cases (n = 18), no multivariate analysis was performed.

Of 151 patients registered at the RFTC during the study period, 125 were included in the final analysis. Twenty-six patients were excluded: 6 refused participation at the time of interview, and 20 had incomplete data (questionnaire not completed or blood sample not obtained during the scheduled dialysis session, due to logistical constraints or temporary patient unavailability). These exclusions reflect inherent constraints of data collection in a clinical setting and may introduce moderate selection bias: the most severely ill patients or those with the least access to care may be underrepresented.

The male-to-female sex ratio was 3.46 (77.6% male). Mean age was 50.7 ± 12.7 years (range: 23 - 78; median: 52 years). The predominant age group was 50 - 59 years (30.4%). Almost all patients (99.2%) were Congolese nationals and Christian (99.2%). Secondary education was the most frequent (76.8%). Most patients were single (52.0%) or in common-law unions (28.8%) (Table 1).

Table 1. Sociodemographic characteristics of the study population (n = 125).

Hypertension was present in 98.4% of patients (n = 123), diabetes in 19.2% (n = 24), cardiac disease in 13.6% (n = 17), stroke in 10.4% (n = 13), and HIV co-infection in 2.4% (n = 3). Alcohol consumption was reported by 44.8% and tobacco use by 14.4%.

Blood transfusion was the most frequently reported dialysis-related risk factor (97/125 patients, 77.6%), followed by piercing (12.0%) and tattooing (8.8%). All patients had end-stage CKD (stage 5). The majority (68.8%) had been on hemodialysis for less than one year. Regarding vascular access, 56 patients (44.8%) used a permanent catheter (PC), 44 (35.2%) an arteriovenous fistula (AVF), and 25 (20.0%) a temporary catheter (TC). All 125 patients received three sessions per week of four hours each (Table 2).

Table 2. Clinical and therapeutic characteristics of the study population (n = 125).

Eighteen patients (14.4%) were anti-HCV seropositive, with perfect concordance between the RDT and confirmatory ELISA (concordance rate: 100%). One hundred and seven patients (85.6%) were seronegative. HCV RNA was not measured in this study; therefore, anti-HCV seropositivity reflects prior or ongoing exposure to HCV without allowing distinction between active infection and spontaneously resolved past infection.

HCV-seropositive patients (n = 18) had a mean age of 51.2 ± 13.9 years (range: 28 - 78). The majority were male (66.7%), had secondary education (61.1%), and were single (50.0%). All seropositive patients were hypertensive (100%) and 83.3% (n = 15) had a history of blood transfusion. Alcohol consumption was reported by 44.4%. Most (72.2%) had been on hemodialysis for less than one year and used either a permanent catheter (38.9%, n = 7) or a temporary catheter (33.3%, n = 6); only 27.8% (n = 5) had an AVF (Table 3).

Table 3. Profile of HCV-seropositive patients (n = 18).

Univariate analysis identified no statistically significant association between anti-HCV seropositivity and any of the studied variables. All odds ratios had wide confidence intervals, reflecting the very limited statistical power due to the small number of positive cases (n = 18). These results should be interpreted as strictly preliminary and do not allow conclusions about the presence or absence of individual risk factor associations. Key results are summarized in Table 4.

Table 4. Univariate analysis: factors associated with anti-HCV seropositivity (n = 125).

TC: temporary catheter; PC: permanent catheter; AVF: arteriovenous fistula; OR: crude odds ratio; 95% CI: 95% confidence interval. Calculated by Fisher’s exact test.

The anti-HCV seroprevalence of 14.4% places the Republic of Congo at an intermediate level on the African hemodialysis spectrum. This value is substantially lower than the pooled African prevalence estimated by Adane and Getawa at 23.04% (95% CI: 18.51 - 27.57) [4], and far below rates reported in Morocco (60% - 76%) [7][19] and Libya (31.1%) [8]. It exceeds figures from Guinea (4.6%) [9] and Cameroon (11.8%) [11], and is consistent with estimates from Nigeria (15%) [10].

Several dialysis-specific factors may explain this intermediate level. The short mean hemodialysis duration (68.8% of patients dialyzed for less than one year) mechanically limits cumulative nosocomial transmission risk, which is known to increase with dialysis vintage [4][18]. Recent improvements in hemovigilance at the National Blood Transfusion Center and the implementation of structured procedures at the RFTC may also have contributed to limiting iatrogenic exposure. Conversely, the high proportion of central venous catheters (64.8% combined PC + TC) constitutes a potential nosocomial risk factor requiring close monitoring, as catheters are recognized as the primary vector of HCV nosocomial transmission in resource-limited dialysis settings [17][18].

The profile of HCV seropositive patients 72.2% catheter-dependent, 83.3% with a blood transfusion history is consistent with the African literature underscoring the predominant role of catheter-based vascular access and polytransfusion in nosocomial HCV transmission in dialysis [4][11][17]. The finding that 72.2% of seropositive patients had been on hemodialysis for less than one year suggests that nosocomial contamination can occur early after dialysis initiation, within the first weeks, in line with the observation by Adane and Getawa of an acquisition odds ratio of 1.44 per additional year on dialysis [4].

The higher proportion of AVF among seronegative patients (37.4% vs 27.8% among seropositive patients), although not reaching statistical significance due to small numbers, is a trend consistent with recommendations for early AVF creation as a protective factor against nosocomial HCV transmission [18]. Promotion of AVF creation remains a priority prevention measure in this context.

Univariate analysis identified no statistically significant risk factor for anti-HCV seropositivity. These results must be explicitly interpreted as preliminary and must not be taken as evidence of the absence of associations. The small number of positive cases (n = 18) provides very insufficient statistical power to detect associations of moderate magnitude, as evidenced by the wide confidence intervals obtained. Nosocomial transmission is largely determined by collective factors (aseptic practices, shared equipment, disinfection protocols) that are difficult to capture through individual questionnaires. Uncollected variables including prior surgical procedures, invasive dental care, and ritual scarification may also play a role. Multicenter studies with larger samples and longitudinal follow-up are needed to identify individual risk factors for HCV seropositivity in this context.

The perfect concordance (100%) between the RDT and confirmatory ELISA demonstrates the reliability of the immunochromatographic RDT used for HCV screening in this population. This result is consistent with manufacturer data and published evaluations of third-generation anti-HCV RDTs [3][19], and supports the use of RDT as a first-line screening tool in African dialysis units where ELISA is not always available in real time. It should be noted, however, that neither the RDT nor the ELISA can distinguish active from resolved past infection: HCV RNA testing by PCR would have been required to assess the prevalence of active infection, which constitutes an important limitation of this study.

Strengths of this study include prospective data collection; perfect RDT-ELISA concordance confirming diagnostic reliability; and the generation of the first published HCV data in the Congolese hemodialysis setting.

Limitations include: I) single-center design restricting generalizability; II) final sample size (n = 125) below the calculated minimum (n = 160), reducing statistical power and the interpretability of risk factor analysis, whose results must be regarded as purely preliminary; III) absence of HCV RNA testing and genotyping due to financial constraints, preventing distinction between active and resolved infection; IV) cross-sectional design precluding causal inference; V) potential selection bias related to 20 exclusions for incomplete data.