Sensitivity of different RT-qPCR solutions for SARS-CoV-2 detection.

OBJECTIVES: The ongoing COVID-19 pandemic continues to impose demands on diagnostic screening. In anticipation that the recurrence of outbreaks and the measures for lifting the lockdown worldwide may cause supply chain issues over the coming months, this study assessed the sensitivity of a number of one-step retrotranscription and quantitative polymerase chain reaction (RT-qPCR) solutions to detect SARS-CoV-2. METHODS: Six different RT-qPCR alternatives were evaluated for SARS-CoV-2/COVID-19 diagnosis based on standard RNA extractions. The one with best sensitivity was also assessed with direct nasopharyngeal swab viral transmission medium (VTM) heating; thus overcoming the RNA extraction step. RESULTS: A wide variability in the sensitivity of RT-qPCR solutions was found that was associated with a range of false negatives from 2% (0.3-7.9%) to 39.8% (30.2-50.2%). Direct preheating of VTM combined with the best solution provided a sensitivity of 72.5% (62.5-81.0%), in the range of some of the solutions based on standard RNA extractions. CONCLUSIONS: Sensitivity limitations of currently used RT-qPCR solutions were found. These results will help to calibrate the impact of false negative diagnoses of COVID-19, and to detect and control new SARS-CoV-2 outbreaks and community transmissions.

High delayed mortality after the first episode of Clostridium difficile infection.

Clostridium difficile infection (CDI) is characterized by a high delayed and unrelated mortality. Predicting delayed mortality in CDI patients could allow the implementation of interventions that could reduce these events. A prospective multicentric study was carried out to investigate prognostic factors associated with mortality. It was based on a cohort (July 2015 to February 2016) of 295 patients presenting with CDI. Logistic regression was used and the model was calibrated using the Hosmer-Lemeshow test. The mortality rate at 75 days in our series was 18%. Age (>65 years), comorbidity (defined by heart failure, diabetes mellitus with any organ lesion, renal failure, active neoplasia or immunosuppression) and fecal incontinence at clinical presentation were associated with delayed (75-day) mortality. When present, each of the aforementioned variables added one point to the score. Mortalities with 0, 1, 2 and 3 points were 0%, 9.4%, 18.5% and 38.2%, respectively. The area under the ROC curve was 0.743, and the Hosmer-Lemeshow goodness-of-fit test p value was 0.875. Therefore, the prediction of high delayed mortality in CDI patients by our scoring system could promote measures for increasing survival in suitable cases.