Twice-weekly rapid COVID tests may be better than infrequent PCR

News brief

A study today in BMJ Open involving the Japan Professional Football League suggests that frequent COVID-19 rapid antigen testing (RAT) can better detect positive SARS-CoV-2 Omicron infections than infrequent polymerase chain reaction (PCR) testing, despite the latter's higher sensitivity.

Researchers from Osaka University compared the sensitivity of COVID-19 RATs with that of PCR tests among 1,759 soccer players and 1,864 staff members.

RATs and PCR tests were conducted twice weekly on the same day, "making this data set uniquely useful to assess the comparative sensitivity of these tests," senior author Seiya Imoto, PhD, of the University of Tokyo, said in an Osaka University news release. A total of 35,393 RATs were performed. Additional voluntary antigen and PCR testing were conducted in clubs with infected players.

10% positive on both rapid, PCR tests

The team analyzed 656 RAT and PCR results collected from Jan 12 to Mar 2, 2022. Sixty-five tests were positive on both RAT and PCR, 38 were negative on RAT and positive on PCR, 1 was positive on RAT and negative on PCR, and 552 were negative on both.

RAT sensitivity was 0.63, and specificity was 0.998. Sensitivity didn't vary significantly by interval between symptom onset and testing, symptom status, or vaccination status.

Sensitivity is the probability that a test correctly identifies all positive cases; the higher the sensitivity, the lower the likelihood of false-negative results. Specificity is the ability to identify those who don't have a condition; the higher the specificity, the lower the risk of false-positive results.

The results, the authors said, suggest that, as with previous variants, frequent RAT testing for Omicron outperforms infrequent PCR testing. While RATs require a larger volume of virus for a true positive result than PCR tests, they are cheaper and generate results quickly.

Study highlights risk of infection from colonization with resistant bacteria

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A review and meta-analysis finds that the risk of an antibiotic-resistant infection in patients colonized with drug-resistant gram-negative bacteria is around 14%, Dutch and German researchers reported yesterday in The Lancet Infectious Diseases.

For the study, a team led by researchers with the Amsterdam University Medical Centers reviewed studies published from 1995 to March 2022 that measured the incidence of infections with multidrug-resistant gram-negative bacteria (MDR-GNB) and vancomycin-resistant enterococci (VRE), including only studies that reported length of follow-up. Their aim was to quantify the effect of gut or urinary colonization with MDR-GNB and VRE on the subsequent risk of infection from these multidrug-resistant pathogens.

Of 301 studies reviewed, 44 (26 on MDR-GNB, 14 on VRE, and 4 on both) involving 14,049 patients from 14 countries were included, 40 of which were analyzed with meta-regression. The pooled cumulative incidence of infection was 14% (95% confidence interval [CI], 10% to 18%) at a median follow-up of 30 days for MDR-GNB and 8% (95% CI, 5% to 13%) at 30 days for VRE.

Infection incidence density (4.26 infections per 1,000 patient-days) and cumulative incidence of infection (19%; 95% CI, 15% to 25%) were highest for carbapenem-resistant Enterobacterales (CRE) at 30 days. Cumulative incidence of infection with extended-spectrum beta-lactamase–producing Enterobacterales or third-generation cephalosporin-resistant Enterobacterales was 8% (95% CI, 5% to 13%).

The study authors note the risk of infection at 30 days in patients colonized with MDR-GNB, particularly CRE, is similar to the risk of surgical-site infections after contaminated or dirty surgical procedures (18% to 25%).

"These differences imply that screening of patient populations at high risk of colonisation and subsequent adjustment of empirical antimicrobial treatment is of greater clinical relevance in the setting of MDR-GNB than of VRE," they wrote. "Additionally, this comparative analysis of infection risks can help to prioritise future research and implementation of targeted prophylactic interventions, such as decolonisation strategies, by indicating the type of multidrug-resistant bacteria and the patient population carrying the highest infection risk."

Bangladesh reports more Nipah virus cases

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A Bangladeshi health ministry official said at a Jan 29 briefing that eight Nipah virus cases have been reported this year, five of them fatal, according to RisingBD, an online news portal in Bangladesh that publishes in both Bengali and English.

The total is up from three cases, all fatal, reported a week ago, though no details were available about the most recent cases.

Officials suspect that people were sickened after drinking raw date juice, which can be contaminated by the saliva or feces from bats that carry the virus and feed on the date juice. Health officials urged people to avoid drinking raw date juice and to avoid consuming dates that are half-eaten by birds.

Over the past 6 years, Bangladesh has reported just a few Nipah virus infections annually. For example, in 2022 the country reported three cases.

There are no treatments or vaccines for Nipah virus, which often causes severe or fatal infections that involve respiratory problems or encephalitis. The World Health Organization and the Coalition for Epidemic Preparedness Innovations (CEPI) have designated Nipah virus a high-priority pathogen, due to its pandemic and bioterrorism potential.

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