Severe underquantification of HIV-1 group O isolates by major commercial PCR-based assays.

HIV-1 diversity poses major challenges to viral load assays because genetic polymorphisms can impede nucleic acid detection. In addition to the on-going viral diversification within the HIV-1 group M pandemic, HIV-1 genetic diversity is further increased by non-group M infections, such as HIV-1 groups O (HIV-1-O), N and P. We here conducted a systematic evaluation of commercially available PCR assays to detect HIV-1-O isolates. We collected 25 primary HIV-1-O isolates covering all genetic clusters within HIV-1-O. Subsequently, this panel of isolates was tested on eight commercially available quantitative and five qualitative HIV-1 PCR-based assays in serial dilutions. Sequence analyses were performed for severe cases of underquantification or lack of detection. We observed differences between the assays in quantification that depended on the HIV-1-O isolate's subgroup. All three tested HIV-1-O subgroup IV isolates were underquantified by the Roche CAP/CTM >800-fold compared to the Abbott RealTime assay. In contrast, the latter assay underquantified several subgroup I isolates >200-fold. Notably, the Xpert HIV-1 Viral Load test from Cepheid failed to detect two of the HIV-1-O isolates, whereas the Roche Cobas 8800 assay readily detected all isolates. Comparative sequence analyses identified polymorphisms in the HIV-1-O long-terminal repeat and integrase genes that likely underlie inadequate nucleic acid amplification. Potential viral load underquantification should be considered in therapeutic monitoring of HIV-1-O-infected patients. Pre-clinical assessments of HIV-1 diagnostic assays could be harmonized by establishing improved and internationally standardized panels of HIV-1 isolates that cover the dynamic diversity of circulating HIV-1 strains.

Laboratory diagnosis of congenital CMV infection in newborns: Impact of pre-analytic factors.

BACKGROUND: To identify infants with congenital cytomegalovirus (cCMV) saliva polymerase chain reaction (PCR) is an ideal screening method. However, there are only few data on the influence of pre-analytic factors on the analytical sensitivity of the CMV PCR. OBJECTIVES: This study aimed to evaluate the performance of different swabbing materials, transport time and initial virus concentration regarding to the efficacy of recovery of CMV-DNA. STUDY DESIGN: Two CMV suspensions containing a high or low concentration of the laboratory strain AD 169 were prepared as test samples. Sampling was simulated by immersion of different swabs in these CMV suspensions and storing the swabs dry or in specified transport media. Transport conditions were modeled by storing the samples for defined time periods prior to DNA extraction and quantitative PCR analyses. Parallel analyses in two different laboratories allowed determination of lab to lab consistency. RESULTS: The duration of storage under the conditions analysed did not have a major effect on the recovery efficiency for the swabbing materials tested. With exception of flocked dry swabs, all tested swabbing materials demonstrated good recovery of CMV DNA. The flocked swab/eNAT system showed the best overall performance. CONCLUSIONS: All tested swabbing materials (with exception of the flocked dry swabs) seem to be well suited for recovery of CMV DNA and appropriate for use for the diagnosis of cCMV infection in symptomatic cases and in general cCMV screening programs of newborns.