Evaluation of the Elecsys SARS-CoV-2 antigen assay for the detection of SARS-CoV-2 in nasopharyngeal swabs.

AIMS: The aim of this study was to evaluate the performance of the automated Elecsys® SARS-CoV-2 antigen assay compared to RT-PCR taken as the gold standard for SARS-CoV-2 detection. METHODS: 225 nasopharyngeal swabs were randomly collected among which 123 were tested positive and 102 negatives for SARS-CoV-2 based on RT-PCR. Antigen dosing were performed on a Cobas 8000 e801 analyzer. RESULTS: The antigen test diagnosed SARS-CoV-2 infection status with an overall sensitivity of 65,85% (95% CI 56,76-74,16%), a specificity of 100% (95% CI 96,49-100%) with a Cut-off value ≥ 1. When the cut-off value for the antigen assay was set to > 0,673 COI, the accuracy reached its highest level with a sensitivity of 74,8% (95% CI 66,2 - 82,2%) and a specificity of 97,1% (95% CI 91,6 - 99,4%). Imprecision was estimated in accordance with manufacturer's claims. CONCLUSIONS: We obtained an overall sensitivity of 65,85% (95% CI 56,76-74,16%) and a specificity of 100% (95% CI 96,49-100%), slightly higher than the results reported by the manufacturer. Yet, it remains relatively low comparatively to what is generally acceptable for these antigenic assays (a relative sensitivity of 80%). We also noticed that the accuracy could reach its highest level if the cut-off is set above 0,673 which is lower than established by the manufacturer. Thus, our results suggest that the Elecsys® SARS-CoV-2 Antigen assays, should be improved prior to be used in a SARS-Cov-2 screening strategy. However, if one antigenic assay could demonstrate acceptable performance, it might be centralized in clinical laboratories, keeping the RT-PCR in a second phase for confirmation.

Prospective Evaluation of Serum ß-Glucan Testing in Patients With Probable or Proven Fungal Diseases.

Background. Early diagnosis and treatment are crucial in invasive fungal diseases (IFD). Serum (1-3)-ß-d-glucan (BG) is believed to be an early IFD marker, but its diagnostic performance has been ambiguous, with insufficient data regarding sensitivity at the time of IFD diagnosis (TOD) and according to outcome. Whether its clinical utility is equivalent for all types of IFD remains unknown. Methods. We included 143 patients with proven or probable IFD (49 invasive candidiasis, 45 invasive aspergillosis [IA], and 49 rare IFD) and analyzed serum BG (Fungitell) at TOD and during treatment. Results. (1-3)-ß-d-glucan was undetectable at TOD in 36% and 48% of patients with candidemia and IA, respectively; there was no correlation between negative BG results at TOD and patients' characteristics, localization of infection, or prior antifungal use. Nevertheless, patients with candidemia due to Candida albicans were more likely to test positive for BG at TOD (odds ratio = 25.4, P = .01) than patients infected with other Candida species. In 70% of the patients with a follow-up, BG negativation occurred in >1 month for candidemia and >3 months for IA. A slower BG decrease in patients with candidemia was associated with deep-seated localizations (P = .04). Thirty-nine percent of patients with rare IFD had undetectable BG at TOD; nonetheless, all patients with chronic subcutaneous IFD tested positive at TOD. Conclusions. Undetectable serum BG does not rule out an early IFD, when the clinical suspicion is high. After IFD diagnostic, kinetics of serum BG are difficult to relate to clinical outcome.

Evaluation of the RAPIDEC® CARBA NP, the Rapid CARB Screen® and the Carba NP test for biochemical detection of carbapenemase-producing Enterobacteriaceae.

OBJECTIVES: The objective of this study was the evaluation of the performance of two commercially available biochemical tests for the rapid detection of carbapenemase-producing Enterobacteriaceae compared with a home-made technique. METHODS: A collection of 150 enterobacterial isolates, including 132 isolates with decreased susceptibility to at least one carbapenem molecule, were tested for carbapenemase activity using the RAPIDEC(®) CARBA NP (bioMérieux), the Rapid CARB Screen(®) (Rosco Diagnostica) and the home-made Carba NP test. This strain collection included 55 non-carbapenemase producers, 21 KPC producers, 21 NDM producers, 17 VIM producers, 11 IMP producers, 16 OXA-48 producers and 9 OXA-48-like producers (OXA-162, OXA-181, OXA-204, OXA-232 and OXA-244). RESULTS: The RAPIDEC(®) CARBA NP detected all carbapenemase producers except a single OXA-244 producer. Using the Rapid CARB Screen(®), one KPC-2, two NDM-1, one OXA-48 and five OXA-48 variant producers gave equivocal results and one OXA-244 producer was not detected. Using the Carba NP test, the same OXA-244 producer was not detected and one OXA-181 producer and one OXA-244 producer gave equivocal results. Sensitivity and specificity were 99% (95% CI 94.3%-99.8%) and 100% (95% CI 93.5%-100%), respectively, for the RAPIDEC(®) CARBA NP test, 89.5% (95% CI 81.7%-94.2%) and 70.9% (95% CI 57.9%-81.2%) for the Rapid CARB Screen(®) and 96.8% (95% CI 91.1%-98.9%) and 100% (95% CI 93.5%-100%) for the Carba NP test. The impact of the use of an adequate bacterial inoculum for obtaining the optimal performance with the RAPIDEC(®) CARBA NP was noted. CONCLUSIONS: The RAPIDEC(®) CARBA NP possesses the best performance for rapid and efficient detection of carbapenemase-producing Enterobacteriaceae.