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Occult hepatitis B infection (OBI), the presence of low hepatitis B virus (HBV) deoxyribonucleic acid (DNA) levels in patients without detectable hepatitis B surface antigen (HBsAg), has significant implications for understanding the natural history of hepatitis B infection. We determined the prevalence of OBI in African patients using a sensitive polymerase chain reaction (PCR) assay and describe here the characteristics of OBI in an urban African hospital population. Routine serological testing as well as molecular studies were performed on sera from 314 patients who were part of a previous study from an urban hospital emergency room in Kampala, Uganda, detecting HBV DNA using a nested PCR with amplification of two regions of the HBV genome. HBV viral loads (VL) were determined by real-time PCR (rtPCR) and sequencing performed to determine HBV genotype and S gene mutations. Among 314 subjects tested, 50 (16%) had chronic HBV infection, 94 (30%) had detectable HBV DNA despite testing HBsAg negative (OBI), and 170 (54%) were not infected. VLs of OBI subjects were relatively low although 19 (20%) had VL exceeding 10(4) IU ml(-) . Subjects with chronic HBV infection had a higher median VL compared to OBI patients (P

Occult hepatitis B infection (OBI), the presence of low hepatitis B virus (HBV) deoxyribonucleic acid (DNA) levels in patients without detectable hepatitis B surface antigen (HBsAg), has significant implications for understanding the natural history of hepatitis B infection. We determined the prevalence of OBI in African patients using a sensitive polymerase chain reaction (PCR) assay and describe here the characteristics of OBI in an urban African hospital population. Routine serological testing as well as molecular studies were performed on sera from 314 patients who were part of a previous study from an urban hospital emergency room in Kampala, Uganda, detecting HBV DNA using a nested PCR with amplification of two regions of the HBV genome. HBV viral loads (VL) were determined by real-time PCR (rtPCR) and sequencing performed to determine HBV genotype and S gene mutations. Among 314 subjects tested, 50 (16%) had chronic HBV infection, 94 (30%) had detectable HBV DNA despite testing HBsAg negative (OBI), and 170 (54%) were not infected. VLs of OBI subjects were relatively low although 19 (20%) had VL exceeding 10(4) IU ml(-) . Subjects with chronic HBV infection had a higher median VL compared to OBI patients (P 0.001). All chronic HBV sequenced (10) and 83/89 OBI sequences were genotype A, the remaining six being genotype D. S-gene mutations were present in some but not all OBI patients (48%). OBI is more prevalent among African patients than previously thought. This may have implications for clinical management and transfusion-related HBV transmission.

Most hepatitis C testing in Uganda is performed using commercial rapid strip assays (RSA) to detect antibodies to hepatitis C virus (anti-HCV), rather than enzyme immunoassays (EIA). The prevalence of hepatitis C antibodies in a Ugandan hospital population was determined using both methods to test their accuracy using nucleic acid testing (NAT) as a reference. Sera from 380 consecutive hospitalized Ugandan patients were tested for anti-HCV using an RSA in Uganda, with subsequent automated third-generation EIA testing in the United States, followed by NAT. Recombinant immunoblot assays (RIBA) were used as a supplementary test to detect anti-HCV epitopes. Overall, anti-HCV was detected in 48/380 (13%) by one or both antibody tests. Anti-HCV was detected in 19 (5.0%) patients by RSA and in 33 (8.7%) patients by EIA; only four patients were anti-HCV positive by both methods. Fourteen of the 48 anti-HCV positive patients had detectable serum HCV RNA, 7 each by bDNA assay or by PCR. RSA detected only 7 of 14 HCV RNA positive sera. Of 29 RNA negative but anti-HCV positive patients tested by RIBA, only two were anti-HCV positive; 27 were anti-HCV negative or indeterminate. Anti-HCV testing by RSA and/or EIA was neither sensitive nor specific for detection of ongoing HCV infection in hospitalized Ugandan patients. Our findings underscore the importance of confirmatory nucleic acid testing, which, despite its increased cost, appears essential to manage African patients with HCV.

Commercially available rapid strip assays (RSAs) for hepatitis B surface antigen (HBsAg) are used for most routine clinical testing in sub-Saharan Africa. This study evaluated the validity of RSA and a more sophisticated enzyme immunoassay (EIA) with confirmation by nucleic acid testing (NAT) in hospitalized patients in Uganda. Sera from 380 consecutive patients collected and tested for HBsAg and anti-HIV in Kampala, Uganda by RSA were sent frozen to Dallas for EIA including HBsAg, total anti-hepatitis B core, hepatitis B e antigen, and anti-HIV. NAT was performed on all HBsAg-positives and on a random sample of 102 patients that were HBsAg-negative by both assays. Overall, 31 (8%) were HBsAg positive by RSA while 50 (13%) were HBsAg-positive by EIA; 26 were concordant between the two assays. Of 55 HBsAg-positive patients, nearly all showed detectable serum hepatitis B virus (HBV) DNA by bDNA (46) or PCR (4) assay. The 26 patients who were HBsAg positive by both EIA and RSA had significantly higher median serum HBV DNA levels than the 24 patients who were HBsAg positive by EIA alone. An additional 12/102 (12%) HBsAg negative patients had very low serum HBV DNA levels by NAT. Several differences in expected results of serologic testing were observed in this large series of African patients. RSA HBsAg testing is less sensitive than EIA; even EIA failed to detect all HBV DNA positive sera. A more complex testing protocol than RSA alone will be needed in Africa to improve patient care.