ABSTRACT
Hepatitis Delta Virus (HDV) infection in HBV‐infected individuals is associated with severe clinical outcomes, and screening is recommended in HBsAg‐positive patients. We used a rapid lateral flow assay (LFA) to assess anti‐HDV antibodies in Brazil, where HDV is highly endemic in the North, while data from the Southeast, particularly São Paulo, remain limited. We conducted a retrospective cross‐sectional study to assess anti‐HDV antibodies among 46 HBsAg‐positive blood donors at Fundação Pró‐Sangue/Hemocentro de São Paulo, 381 patients with chronic hepatitis B from the Central Laboratory Division of HC‐FMUSP, and 189 individuals from the Hepatology Clinic of HC‐FMUSP (101 HIV‐infected and 88 chronically HBV‐infected). Anti‐HDV antibodies were detected using a validated LFA. Positive controls (n = 24) included samples previously confirmed by ELISA and/or PCR, predominantly infected with HDV genotypes 3 and 8. Among 443,400 blood donations, 48 (0.01%) were positive for at least two HBV markers; of these, 46 were tested for HDV, and all were anti‐HDV negative. All 381 patients undergoing HBV viral load monitoring were anti‐HDV negative, as were all 189 patients receiving hepatology care, including those with HIV coinfection or advanced liver disease. The LFA correctly identified all control samples positive for both anti‐HDV antibodies and HDV RNA. The absence of detectable anti‐HDV among diverse at‐risk populations in São Paulo is consistent with the low endemicity of HDV infection in southeastern Brazil. These findings, together with the assay's high specificity in HDV RNA‐positive controls, support its potential utility as a screening tool for HDV infection in low‐prevalence settings.
Keywords: blood donors, chronic hepatitis B, HBV, HDV, rapid lateral flow assay
1. Introduction
Hepatitis D virus (HDV) infection occurs exclusively in individuals infected with hepatitis B virus (HBV) and is associated with a more aggressive course of liver disease. HBV/HDV coinfection accelerates progression to cirrhosis and hepatocellular carcinoma and significantly increases mortality compared with HBV monoinfection [1, 2]. HDV is a defective, single‐stranded RNA virus that depends on the HBV surface antigen (HBsAg) for viral assembly and entry into hepatocytes. It has the smallest known genome among human pathogens and encodes only the hepatitis delta antigen [3, 4, 5, 6].
It is estimated that approximately 254 million people worldwide are living with chronic HBV infection, and nearly 5% of HBsAg‐positive individuals are coinfected with HDV [7, 8, 9]. A marked geographic variability in HDV prevalence has been observed, with several high‐prevalence hotspots identified, notably in Mongolia (36.9%), in the Republic of Moldova, and in countries in western and central Africa (> 10%) [8, 10]. In Brazil, the prevalence of HBV has been declining nationwide, classifying the country as having low endemicity, with prevalence below 1%. However, localized areas of high HBV prevalence persist, particularly in the Amazon region [11]. Several studies have shown that HDV cases are predominantly concentrated in the Amazon Basin in Northern Brazil, while data from other regions, including the Southeast, remain limited [12, 13].
Despite its significant clinical impact, HDV infection remains underdiagnosed, largely due to limited access to diagnostic testing, lack of routine screening among HBsAg‐positive individuals, and low clinical awareness, particularly in low‐ and middle‐income countries. International guidelines recommend HDV screening in all HBsAg‐positive individuals through serological testing for anti‐HDV antibodies followed by confirmation with HDV RNA assays [7, 14, 15]. However, the lack of systematic screening, combined with limited availability and standardization of PCR‐based assays, often leads to delayed diagnosis, frequently at advanced stages of liver disease [16].
The implementation of screening strategies based on reflex testing has been proposed as an effective and feasible approach to improve early detection of HDV infection and to generate more accurate estimates of disease prevalence [17]. Early diagnosis also enables appropriate referral for clinical follow‐up, counselling, and therapeutic interventions, which is particularly important given the limited treatment options currently available, despite the emergence of novel antiviral agents [2, 18, 19, 20, 21].
In this context, rapid, affordable and accessible diagnostic tools, such as immunochromatographic assays, have emerged as promising alternatives to expand HDV screening, especially in regions with limited laboratory infrastructure [8, 22]. Therefore, this study aimed to evaluate the prevalence of HDV infection among blood donors and patients with chronic hepatitis B in São Paulo, Brazil, using a rapid lateral flow test to detect anti‐HDV antibodies [22]. By addressing existing epidemiological gaps, these findings may contribute to improved screening strategies and public health policies targeting HBV/HDV coinfection in Brazil.
2. Materials and Methods
2.1. Study Design and Population
This retrospective cross‐sectional study included HBsAg‐positive blood donors from Fundação Pró‐Sangue/Hemocentro de São Paulo (FPS‐HSP), as well as patients with chronic hepatitis B from the Central Laboratory Division of the Hospital das Clínicas and Faculty of Medicine (DLC‐HC‐FMUSP), and from Hepatology Clinic at the Hospital das Clínicas, Faculty of Medicine (Hepatology‐HC‐FMUSP). The study groups were defined according to distinct inclusion criteria, and no overlap occurred between the groups (Table 1). This study assessed the frequency of HDV serologic markers, and the protocol was approved by the Research Ethics Committee (Plataforma Brasil No. 76681723.0.0000.0068).
TABLE 1.
Study populations, origin and inclusion characteristics.
| Group | Origin | Population included | Inclusion criteria | Subgroups/characteristics | Period/notes |
|---|---|---|---|---|---|
| Blood donors (FPS‐HSP) | Fundação Pró‐Sangue/Hemocentro de São Paulo | 46 HBsAg‐positive blood donors | ≥ 2 HBV markers (HBsAg, anti‐HBc and/or HBV DNA) | Sociodemographic data collected | Jan 2020–Dec 2023 |
| Chronic HBV patients (DLC‐HC‐FMUSP) | Central Laboratory, Hospital das Clínicas FMUSP | 381 chronic HBV patients undergoing treatment | HBsAg‐positive referred for HBV viral load testing | Sociodemographic data collected | Aug 2023–Oct 2023 |
| Chronic HBV patients (Hepatology‐HC‐FMUSP) | Hepatology outpatient clinic, HC‐FMUSP | 88 chronic HBV with liver disease complications | HBsAg‐positive under clinical follow‐up | 48 hepatocellular carcinoma; 27 cirrhosis; 13 fibrosis | Biorepository 2017 |
| HIV patients with serological markers of HBV infection | Hepatology‐HC‐FMUSP | 101 HIV patients with serological markers of HBV infection | Anti‐HBc and/or HBsAg positive | 11 HBsAg+; 70 anti‐HBc/anti‐HBs+; 20 anti‐HBc only | Biorepository 2012 |
2.2. Blood Donors at FPS‐HSP
Stored/frozen serum samples collected between January 2020 and December 2023 from blood donors of FPS‐HSP who tested reactive or positive for at least two HBV markers during screening (HBsAg, anti‐HBc and HBV DNA) were included in this study. Sociodemographic data were also collected.
Routine screening involved serological assays for HIV‐1/2, HBV, HCV, syphilis, HTLV‐1/2 and Chagas disease, combined with nucleic acid amplification testing (NAT) for HIV, HCV and HBV. HBV screening was performed using two chemiluminescent immunoassays (CMIA) (Architect/Alinity, Abbott, Wiesbaden, Germany) for HBsAg and anti‐HBc detections, along with NAT (Bio‐Manguinhos/FIOCRUZ, Brazil) for HBV DNA detection.
2.3. Hepatitis B Patients From DLC‐HC‐FMUSP
The study involved 381 samples from chronic HBV patients undergoing treatment and viral load monitoring across multiple healthcare facilities across São Paulo, including hospitals, clinics and primary care centers, as part of the Ministry of Health's viral load monitoring network. These samples were transported via the health system's logistics network to the DLC‐HC‐FMUSP for HBV viral load quantification. Of these, 381 stored samples collected between August and October 2023 were included in this study. Epidemiological data were extracted from medical records to complement the analysis.
As part of the routine workflow HBV viral load quantification was performed using the Alinity m HBV system (Abbott Molecular Inc., Des Plaines, Illinois, USA).
2.4. HIV‐Infected and Chronic Hepatitis B Patients From Hepatology‐HC‐FMUSP
This study included samples from 101 HIV‐infected patients with serological markers of HBV infection and 88 patients with chronic HBV infection who were followed at the Hepatology Division of HC‐FMUSP. Among the HIV‐infected patients, 11 were positive for both anti‐HBc and HBsAg, 70 were positive for both anti‐HBc and anti‐HBs, and 20 were positive for anti‐HBc only. Among the 88 patients with chronic HBV infection, all were HBsAg‐positive; 48 had hepatocellular carcinoma, 27 had cirrhosis, and 13 had liver fibrosis (Table 1).
The samples were obtained from the Biological Material Biorepository. All participants had previously provided written informed consent for the future use of their samples in research under protocols approved by the institutional ethics committee in 2012 and 2017, with CAAE numbers 04721712.4.0000.0068 and 65279016.8.1001.0068, respectively.
2.5. Lateral Flow Assay (LFA)
HBsAg‐positive samples were tested for antibodies against HDV (anti‐HDV) using a Lateral Flow Assay (LFA), a rapid diagnostic test developed and validated by Lempp et al. [22], which demonstrated a sensitivity of 94.6% (314/332; 95% CI, 91.6%–96.5%) and a specificity of 100% (142/142; 95% CI, 97.4%–100%). The assay was performed according to the established protocol. Briefly, serum samples (10 μL) were diluted at 1:8 in running buffer pre‐warmed to 37°C or room temperature, to a final volume of 80 μL. Running buffer was prepared with 0.3% casein in 1× phosphate‐buffered saline (PBS) and stored in aliquots at −20°C until use. The diluted samples were applied to the sample pad of the test strips, and the results were recorded after 20 min.
As positive controls, we selected 24 samples with anti‐HDV seroreactivity and/or detectable HDV RNA. Anti‐HDV antibodies were detected using the ETI‐AB‐DELTAK‐2 competitive ELISA assay (DiaSorin), and HDV RNA was detected by conventional polymerase chain reaction (PCR). Among the HDV RNA‐positive samples, 13 were identified as genotype HDV‐3, one as genotype HDV‐8, and one could not be genotyped because the viral load was below the limit of quantification. All assays were performed according to the manufacturer's instructions and the protocols established at the laboratory of the School of Medicine, University of São Paulo. The characteristics of the positive control samples, including ELISA, PCR and genotype results, are summarized in Table 2.
TABLE 2.
Performance of a lateral flow assay (LFA) for anti‐HDV detection in positive control samples characterized by ELISA, PCR and genotype.
| Sample | Anti‐HDV (ELISA) | ELISA OD | ELISA cut‐off | ELISA interpretation | HDV RNA (PCR) | HDV genotype | LFA (anti‐HDV) |
|---|---|---|---|---|---|---|---|
| PC1 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC2 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC3 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC4 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC5 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC6 | Positive | 0.001 | ≤ 0.770 | Strong reactivity | Positive | 8 | Positive |
| PC7 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC8 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC9 | Positive | 0.621 | ≤ 0.770 | Low‐level reactivity | Negative | Not tested | Negative |
| PC10 | Positive | 0.483 | ≤ 0.870 | Moderate reactivity | Negative | Not tested | Negative |
| PC11 | Positive | 0.733 | ≤ 0.870 | Borderline reactivity | Negative | Not tested | Negative |
| PC12 | Positive | NA | NA | NA | Negative | Not tested | Negative |
| PC13 | Positive | 0.614 | ≤ 1.110 | Moderate reactivity | Negative | Not tested | Negative |
| PC14 | Positive | 0.000 | ≤ 0.700 | Strong reactivity | Positive | 3 | Positive |
| PC15 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC16 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC17 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC18 | Positive | NA | NA | NA | Negative | Not tested | Negative |
| PC19 | Positive | NA | NA | NA | Positive | Not genotyped | Positive |
| PC20 | Positive | NA | NA | NA | Negative | Not tested | Positive |
| PC21 | Positive | NA | NA | NA | Negative | Not tested | Negative |
| PC22 | Positive | NA | NA | NA | Positive | 3 | Positive |
| PC23 | Positive | NA | NA | NA | Negative | Not tested | Negative |
| PC24 | Positive | NA | NA | NA | Positive | 3 | Positive |
Note: ELISA OD and cut‐off values were unavailable for some samples, although anti‐HDV positivity had been previously confirmed.
Abbreviations: LFA, lateral flow assay; NA, not available; PC, positive control; PCR, polymerase chain reaction.
The anti‐HDV prevalence and 95% confidence intervals (95% CIs) were estimated using the Wilson score method in OpenEpi 3.01v.
3. Results
3.1. LFA Of HBsAg‐Positive Blood Donors—FPS‐HSP
Among 443,400 voluntary blood donations collected between January 2020 and December 2023, 47 tested positive for at least two HBV screening markers (HBsAg, anti‐HBc and/or HBV DNA). An additional donation was initially positive for HBV DNA only but was subsequently confirmed as HBsAg‐positive during donor follow‐up and was therefore included in the study. This corresponds to an HBV prevalence of 0.01% (48/443,400; 95% CI: 0.0082%–0.0144%) among all donations during the study period. Of these, 46/48 (96%) samples had sufficient volume for LFA testing, and all were negative for anti‐HDV antibodies.
Donor demographic data showed that 73% were male, with a median age of 43 years (range: 25–67 years). Regarding self‐reported ethnicity, 50% identified as white and 40% as mixed‐race. Additionally, 52% of donors were born in São Paulo, and 87% of the tested samples had detectable HBV DNA (Table S1).
3.2. LFA Of Chronic Hepatitis B Patients From DLC‐HC‐FMUSP
The study analysed 381 consecutive stored samples from patients with HBsAg‐positive chronic HBV undergoing viral load monitoring at DLC‐HC‐FMUSP, collected between August and October 2023. These samples were tested for anti‐HDV antibodies using the LFA, and all yielded negative results.
Epidemiological data revealed that 52% of the patients were male, with a mean age of 55 years (range: 14–92 years). Additionally, HBV DNA was detectable in 38% of the samples.
3.3. LFA of Chronic Hepatitis B Patients From Hepatology—HC‐FMUSP
We analysed serum samples from 101 HIV‐infected individuals with serological markers of current or previous HBV exposure and 88 patients with chronic HBV infection and advanced liver disease, including hepatocellular carcinoma, cirrhosis, and liver fibrosis. All samples tested negative for anti‐HDV antibodies using the LFA.
3.3.1. Anti‐HDV Seroprevalence in São Paulo Using LFA
Among the 616 participants, including HBsAg‐positive blood donors, HIV‐Infected individuals, and patients with Chronic Hepatitis, no anti‐HDV‐positive cases were identified using LFA. The observed anti‐HDV seroprevalence was therefore 0% (0/616; 95% CI: 0%–0.62%).
3.4. LFA of Positive Controls
As positive controls, 24 samples were used: 15 tested positive for both anti‐HDV antibodies (ELISA) and HDV RNA (PCR), while 9 were positive only for anti‐HDV antibodies (ELISA) and negative for HDV RNA (PCR). The genotypes of the positive controls with detectable HDV RNA included 14 samples of genotype HDV‐3 and one of genotype HDV‐8.
All 24 samples were serologically tested using the LFA for anti‐HDV antibodies. Of the 15 positive controls that were positive for both anti‐HDV by ELISA and HDV RNA, all 15 (15/15, 100%) tested positive by the LFA. Of the nine controls that were positive for anti‐HDV by ELISA but negative for HDV RNA, eight tested negative by the LFA, whereas only one (1/9, 11.1%) yielded a positive LFA result (Tables 2 and 3 and Figure 1). Among the control samples with available ELISA optical density (OD) values, HDV RNA‐positive samples, PC6 and PC14 (Table 2), showed very low OD values in the competitive ELISA, indicating strong anti‐HDV reactivity, and were consistently detected by the LFA. Conversely, ELISA‐positive/HDV RNA‐negative samples, PC9, PC10 and PC11 (Table 2), exhibited OD values closer to the assay cut‐off and were generally not detected by the LFA.
TABLE 3.
Positivity of the lateral flow assay (LFA) for anti‐HDV detection according to anti‐HDV ELISA and HDV RNA status in the control panel.
| Reference status | N | LFA positive, n (%) |
|---|---|---|
| Anti‐HDV ELISA‐positive/HDV RNA‐positive | 15 | 15 (100.0) |
| Anti‐HDV ELISA‐positive/HDV RNA‐negative | 9 | 1 (11.1) |
| Overall anti‐HDV ELISA‐positive controls | 24 | 16 (66.7) |
Note: Anti‐HDV ELISA‐positive/HDV RNA‐positive control samples were detected by the LFA, whereas only 1 of 9 anti‐HDV ELISA‐positive/HDV RNA‐negative samples was positive by LFA.
FIGURE 1.
Representative lateral flow assay (LFA) results for anti‐HDV detection in previously characterized positive control samples (PC1–PC24). Samples labelled as positive (POS) show two bands (control and test lines), indicating the presence of anti‐HDV antibodies, whereas negative samples (NEG) show only the control line. All assays were valid as indicated by the presence of the control band.
4. Discussion
In this study, we evaluated the prevalence of anti‐HDV antibodies among HBsAg‐positive blood donors, patients undergoing routine HBV viral load monitoring, individuals with advanced liver disease, and individuals with HIV coinfection in São Paulo, Brazil, using a validated LFA. No anti‐HDV reactivity detectable was identified in the studied groups, suggesting a low‐HDV‐endemic region, and highlight the pronounced geographic heterogeneity of HDV epidemiology [8, 10, 23]. Data from Brazil indicate that HDV infection is predominantly concentrated in the Northern region, particularly in the Amazon Basin, where prevalence among HBsAg‐positive individuals can exceed 20% [24, 25]. In other regions, such as the Northeast, HDV prevalence ranges from 0.8% to 8.69%, while in the Southeast it ranges from 1.7% to 6.22% [12, 13, 26, 27]. HDV infection in South America is highly heterogeneous, with well‐defined endemic hotspots concentrated in the Amazon Basin, particularly across northern Brazil, Peru, Venezuela, Colombia and parts of Bolivia, while markedly lower prevalence is observed in southern regions of the continent [22].
To our knowledge, this is the first study to evaluate HDV antibodies among blood donors in the Southeast region of Brazil. The absence of anti‐HDV antibodies using LFA, among HBsAg‐positive blood donors at FPS‐HSP is consistent with this population's low‐risk profile. Blood donors constitute a highly selected group, subject to stringent eligibility criteria and comprehensive serological and molecular screening procedures [28]. These measures contribute to the very low observed prevalence of HBV (0.01%) and are likely to limit HDV circulation in this setting. Therefore, the absence of detectable anti‐HDV was expected and further supports the notion that HDV transmission is negligible among blood donors in São Paulo.
Also, no anti‐HDV reactivity was detected among patients with chronic hepatitis B receiving care in public healthcare services, including those referred for HBV viral load monitoring and those followed in hepatology outpatient clinics. The absence of HDV markers even in these higher risk clinical subgroups suggests that HDV does not appear to be a major contributor to the liver disease burden among HBV‐infected individuals in São Paulo. Globally, the estimated prevalence of anti‐HDV among individuals with liver disease attending hepatology clinics is 16.4% [8]. Higher anti‐HDV prevalence has also been reported in other specific populations, including people who inject drugs, patients undergoing haemodialysis, sex workers, men who have sex with men, and individuals coinfected with HCV or HIV, likely reflecting shared transmission routes [8]. In Brazil, evidence from endemic areas further supports this geographically concentrated and risk‐based pattern of HDV transmission. In the Northern region, considered endemic, Silva et al. [29] reported a high frequency of HDV infection among people who inject drugs with detectable HBV DNA: anti‐HDV antibodies were identified in 19.5% of cases, and molecular markers in 11.7%, including HDV genotypes 1 and 3. In contrast, in the metropolitan area of São Paulo, only 1.2% of HIV/HBV‐coinfected patients were found to be anti‐HDV positive [30]. Taken together, these findings reinforce the notion that in endemic settings, HDV transmission may be amplified within specific high‐risk populations, whereas in non‐endemic urban centers such as São Paulo, HDV circulation appears limited.
Widespread HBV vaccination, which also protects against HDV infection, has contributed to changes in the global epidemiology of HDV [10, 14]. In Brazil, recent evidence indicates a decline in HBV prevalence, even in historically endemic areas. A study conducted in the Brazilian Amazon reported a substantial reduction in HBsAg prevalence, from approximately 17%–1.5%, a decline primarily attributed to the expansion of HBV vaccination coverage. Similarly, HDV coinfection was identified in 25% of HBsAg‐positive individuals, compared with a 34% prevalence reported in 1988 [24, 31].
The diagnostic performance of the LFA used in this study also warrants further consideration. All positive control samples with confirmed anti‐HDV antibodies and detectable HDV RNA were correctly identified by the LFA, including samples infected with HDV genotypes 3 and 8 that circulate in Brazil, confirming robust sensitivity across distinct genotypes [22]. The lower detection rate observed among ELISA‐positive but HDV RNA–negative samples likely reflects lower antibody titers, possibly due to resolved infection, potential false‐positive results inherent to the ELISA methodology, and the reduced analytical sensitivity of rapid assays compared with laboratory‐based immunoassays. Nevertheless, for screening purposes—particularly in low‐prevalence settings—the high specificity observed in our study represents a key advantage, as it minimizes false‐positive results and reduces the need for unnecessary confirmatory testing [8, 22].
From a public health perspective, our findings have important implications for HDV screening strategies. International guidelines recommend universal HDV screening for all HBsAg‐positive individuals [7, 15]. However, in low‐prevalence settings such as São Paulo, where very few anti‐HDV‐positive individuals are expected to be identified, universal screening may yield a low diagnostic return while requiring substantial healthcare resources for large‐scale serological testing. In this context, reflex or targeted screening approaches—focusing on individuals originating from endemic areas or those presenting specific epidemiological risk factors—have been proposed as more feasible and resource‐efficient alternatives [32, 33, 34]. Rapid and affordable diagnostic tools, such as the LFA evaluated in this study, may play a pivotal role in expanding access to anti‐HDV screening while optimizing healthcare resource allocation.
This study has some limitations. Its retrospective design and reliance on stored samples limited the availability of detailed epidemiological data, including migration history and behavioral risk factors. No anti‐HDV reactivity detectable by the LFA may reflect the extremely low prevalence of HDV infection in São Paulo; however, the possibility that the LFA failed to detect samples with very low anti‐HDV antibody levels cannot be excluded. Such samples may represent individuals with past resolved HDV infection and low residual antibody titers, although previous studies have also suggested that some low‐level ELISA‐reactive samples may correspond to nonspecific reactivity or false‐positive ELISA results, making their clinical significance difficult to determine.
Furthermore, all cohort samples were screened exclusively using the LFA, without parallel anti‐HDV ELISA testing. Consequently, samples with low‐level anti‐HDV reactivity may have gone undetected by the LFA. A larger sample size and parallel testing with a laboratory‐based ELISA would have strengthened the study and might have identified a small number of additional anti‐HDV‐reactive individuals. However, such an approach could also introduce another challenge, as low‐level ELISA reactivity may reflect nonspecific reactions or false‐positive results, a well‐recognized limitation of ELISA‐based assays that may complicate the interpretation of anti‐HDV seropositivity in low‐prevalence settings. Therefore, further studies, including cost‐effectiveness analyses, are needed to determine whether universal, reflex or risk‐based HDV screening strategies represent the most appropriate approach for low‐prevalence regions such as São Paulo.
Nevertheless, the inclusion of diverse at‐risk populations, including HBsAg‐positive blood donors, HIV‐infected individuals and patients with chronic hepatitis B, together with the use of a previously validated diagnostic assay, strengthens the robustness of our findings. Notably, the performance of the LFA in our control panel was highly consistent with the results reported by Lempp et al., detecting all HDV RNA‐positive samples while failing to identify primarily samples with weak anti‐HDV reactivity close to the ELISA cut‐off. Taken together, these findings support the overall reliability and internal validity of the study and suggest that the LFA is effective for identifying clinically relevant HDV infections associated with active viral replication.
In conclusion, the absence of detectable anti‐HDV seroreactivity using a rapid LFA among HBsAg‐positive blood donors, HIV‐infected individuals, and patients with chronic hepatitis B in São Paulo is consistent with the low endemicity of HDV infection in southeastern Brazil. These findings further highlight the marked geographic heterogeneity of HDV infection across Brazil, with a clear concentration of cases in endemic regions. Together with the assay's high sensitivity and specificity in HDV RNA‐positive controls, the results support the potential utility of rapid LFA‐based testing as a practical screening tool in low‐prevalence settings. These findings also underscore the importance of region‐specific surveillance and diagnostic strategies to improve the detection of HDV infection and inform public health interventions in Brazil.
Conflicts of Interest
The lateral flow assay used in this study incorporates a recombinant hepatitis delta antigen covered by patent family WO2019219840A1, including US Patent No. US11841368B2, assigned to Universität Heidelberg. S.U. is an inventor on this patent. All other authors declare no conflicts of interest.
Supporting information
Table S1: LFA results of 46 HBV‐positive blood donors.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Table S1: LFA results of 46 HBV‐positive blood donors.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.