The Practicability of the Xpert HCV Viral Load Fingerstick Point-of-Care Assay in Primary Care Settings

Linkage to care presents one obstacle toward eliminating HCV, and the current two-step pathway (anti-HCV, followed by HCV-RNA testing) results in the loss of patients. HCV screening was tested in the primary care setting with the fingerstick Xpert HCV viral load point-of-care assay to analyze the practicability of immediate diagnosis. Anti-HCV (Cobas) and HCV-RNA (Cobas Amplicor version 2.0, only performed if anti-HCV was positive) were analyzed centrally as the gold standard. The Xpert assay was performed by 10 primary care private practices. In total, 622 patients were recruited. Five individuals (0.8%) were anti-HCV positive, and one was HCV-RNA positive. The Xpert test was valid in 546/622 (87.8%) patients. It was negative in 544 and positive in 2 cases, both of whom were anti-HCV negative. The HCV-RNA PCR and the Xpert test were both negative in 4/5 anti-HCV-positive cases, and the individual with HCV-RNA 4.5 × 106 IU/mL was not detected by the Xpert test. Primary care physicians rated the Xpert test practicability as bad, satisfactory, or good in 6%, 13%, and 81%, respectively, though 14/29 (48%) bad test ratings were assigned by a single practice. Despite adequate acceptance, interpretability and diagnostic performance in primary care settings should be further evaluated before its use in HCV screening can be recommended.

COVID-19 Antibody Testing of Patients Admitted to the ICU by a Novel, Point-of-Care Assay, and the Relationship to Survival

Diagnosing persons infected by COVID-19 is key to the control of the pandemic. It has, however, become increasingly important to identify those who have had the infection by measurement of circulating antibodies against Sars-COV-2 of the IgM and IgG type. In this report we show the development of a rapid and sensitive point-of-care assay for the measurement of IgG antibodies against the two spike proteins, S1 and S2, of the Sars-COV-2 virus.MethodThe AgPlus electrochemical technology was applied and the S1 and S2 proteins were biotinylated and immobilized onto streptavidin coated magnetic particles as the capture component of the assay. The IgG antibodies bound to the particles were detected by anti-human IgG and the signal expressed as nC (nano Coulomb). Assay time was <10 min.ResultsPlasma (n=211) from 117 SARS-Cov-2 PCR positive patients and from 78 persons with samples taken before the COVID-19 pandemic were analysed. The sensitivity and specificity of the assay were 91.9% and 100%, respectively. The assay was highly correlated to a predicate and FDA-approved IgG antibody ELISA (r=0.81). The IgG response was significantly lower in patients who died during their ICU stay.ConclusionsA poor IgG response after a COVID-19 infection is a serious risk factor as to death. A sensitive, rapid and accurate IgG antibody POC assay should be useful in the daily management and evaluation of COVID-19 infected patients.

Study to evaluate the performance of a point-of-care whole blood HIV viral load test (SAMBA II HIV-1 Semi-Q Whole Blood).

Remote areas of many low and middle income (LMI) countries have poor access to HIV viral load (HIV VL) testing. The SAMBA-II (Simple Amplification-based Assay) Semi-Q Whole Blood Test (Diagnostics for the Real World (DRW), Cambridge, UK) is a point of care assay which uses leucodepletion technology to allow whole blood testing in remote settings. 1540 consecutive HIV-positive clinic patients in Cameroon (250), UK (633), Ukraine (412) and Zimbabwe (245) donated venous blood (all countries) and finger-prick blood (all except UK) for testing on SAMBA-II. SAMBA II results were compared with simultaneous plasma results on the Abbott RealTime HIV-1 (Abbott Molecular, Des Plaines, IL) viral load assay and interpreted as either <1000 RNA copies/ml or ≥1000 RNA copies/ml. For 1528 venous whole-blood samples tested on SAMBA II, overall percent agreement with the reference test at a cut-off of HIV VL ≥1000 cps/ml was 96.9% (1480/1528 95% CI 95.9-97.7), negative percent agreement 97.7% (1259/1289 95% CI 96.7-98.4), positive percent agreement 92.5% (221/239 95% CI 88.4-95.5). For 854 finger-prick samples there was 95.0% (811/854 95% CI 93.3-96.3) overall percent agreement; negative percent agreement 98.0% (625/638, 95% CI 96.5-98.9); positive percent agreement 86.1% (186/216 95% CI 80.8-90.4). These rose to 93.5% (82.1, 98.6), 97.6% (95.6, 98.8) and 95.6% (93.3, 97.3) after exclusion of aberrant results from the Ukraine centre. These results show a high level of agreement between SAMBA-II and a laboratory-based assay. SAMBA-II has a performance that is suitable to use as a VL point of care assay in remote settings