Browsing by Author "Geretti, Anna Maria"

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    Detection of Highly Prevalent Hepatitis B Virus Coinfection among HIV-Seropositive Persons in Ghana
    (American Society for Microbiology, 2010-09) Geretti, Anna Maria; Patel, Mauli; Sarfo, Fred Stephen; Phillips, Richard Odame; Chadwick, David; et.al
    Simple hepatitis B surface antigen (HBsAg) tests may facilitate ascertainment of hepatitis B virus (HBV) infection in settings with high endemicity but limited infrastructure. We evaluated two rapid HBsAg tests and characterized HBV coinfection in a Ghanaian HIV-positive cohort. Samples from 838 patients were tested by the rapid assays Determine and Vikia and the reference assays Architect, Murex version 3, and Liaison Ultra. The assays were also evaluated using the 2nd International Standard, a seroconversion panel, and two mutant panels. HBsAg-positive samples underwent HBV DNA quantification by real-time PCR and surface and polymerase gene population sequencing. Overall, 140/838 patients (16.7%; 95% confidence interval, 14.2 to 19.2%) were HBsAg positive, and of these, 103/140 (73.6%) were e-antigen negative and 118/140 (84.3%) showed an HBV DNA level of >14 IU/ml (median, 8,279 IU/ml). Assay sensitivities and specificities were as follows: Architect, 97.9 and 99.6%; Liaison, 97.1 and 99.4%; Murex, 98.6 and 99.3%; Determine, 69.3 and 100%; and Vikia, 70.7 and 100%. With Determine, the limit of detection was >1.5 to 3.4 HBsAg IU/ml, and the median HBV DNA loads were 598 and 10,905 IU/ml in Determine-negative and -positive samples, respectively (P 0.0005). Results were similar with the Vikia assay. HBV DNA sequencing indicated infection with genotype E in 82/86 (95.3%) patients. HBsAg mutations affected assay performance, including a T123A mutant that escaped detection by Architect. Major drug resistance mutations were observed in 4/86 patients (4.6%). The prevalence of HBV coinfection was high in this HIV-positive Ghanaian cohort. The two rapid assays identified HBsAg-positive patients at risk for liver disease with high specificity, albeit with only moderate sensitivity.
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    Hepatitis C Virus (HCV) RNA screening and sequencing using dry plasma spots
    (Elsevier B.V., 2017-10) Phillips, Richard Odame; Geretti, Anna Maria; King, Simon; Adjei-Asante, Kwabena; Appiah, Lambert Tetteh; et. al
    Background: HCV RNA screening of large sample repositories provides data on HCV epidemic patterns that may help guide control policies. In resource-limited settings, shipment of frozen samples to molecular laboratory facilities and testing of individual samples may be prohibitively expensive. Objective: Our aim was to detect and sequence HCV RNA in a large HIV-positive cohort from Kumasi, Ghana, using pooled and individual dried plasma spots (DPS) produced from samples stored at −80 °C. Study design: In the validation phase, replicate DPS were prepared with six dilutions (500–10,000 IU/ml) of the 4th International Standard for HCV and tested in three independent experiments. In the testing phase, DPS prepared with plasma samples from 875 HIV-positive subjects were pooled for screening, followed by testing of individual DPS of positive pools. Input from individual DPS was two 6 mm punches; pools comprised two punches from each of five DPS. Genotypes were determined by Sanger sequencing of HCV core and NS5B. Results: With the dilution series, sensitivity of HCV RNA detection was ≥2500 IU/ml. Replicate DPS gave intraassay and inter-assay coefficients of variation ≤1.4%. With the stored samples, HCV RNA was detected in 5/175 DPS pools and in one DPS from each positive pool, yielding a HCV RNA prevalence of 5/875 (0.57%; 95% confidence interval 0.07-1.07%). The five samples were sequenced as HCV genotypes 2l and 2r. Discussion: DPS allowed reproducible HCV RNA detection, and pooling effectively contained the cost and labour of screening a previously untested, low-prevalence cohort. DPS were also suitable for HCV sequencing.