Study: COVID-19 rapid home tests not highly sensitive for Omicron

News brief

Dutch researchers reveal that the sensitivities of three commonly used rapid antigen tests, when used in asymptomatic people in the Omicron period, were very low and suggest repeat testing after a negative test. The study is published in Clinical Microbiology and Infection.

The study was conducted between Jan 2 to Mar 30, 2022, when Omicron accounted for 90% to 99.5% of all cases in the Netherlands. A total of 3,600 asymptomatic people with suspected COVID-19 were tested using one of three at-home rapid antigen tests and a reverse-transcription polymerase chain reaction (RT-PCR) test. Home tests were provided within 3 hours of taking an RT-PCR test.

Overall sensitivities for the three home tests were 27.5% (95% confidence interval [CI], 21.3% to 34.3%) for Flowflex, 20.9% (95% CI, 13.9% to 29.4%) for MPBio, and 25.6% (95% CI, 19.1% to 33.1%) for Clinitest. After applying a viral load cut-off, sensitivities increased to 48.3% (95% CI, 37.6% to 59.2%), 37.8% (95% CI, 22.5% to 55.2%), and 40.0% (95% CI, 29.5% to 51.2%), respectively.

Participants with negative tests also filled out a questionnaire, which showed 54.8% retested in the 10 days following a negative test, with 24.6% testing positive.

The positive predictive values were greater than 92%, and negative predictive values were greater than 88% for all self-tests. The authors said previous studies on self-tests conducted before Omicron yielded better sensitivities, at 52.5% in asymptomatic individuals.

"We conclude that SARS-CoV-2 self-testing has limited value for asymptomatic individuals wishing to protect vulnerable persons and may even lead to a false sense of security," the authors concluded. "The high SARS-CoV-2 infection rate within 10 days of a negative RT-PCR test that we found in our study emphasizes the importance of re-testing over time, especially when symptoms develop, to reduce missed infections as much as possible."

Ebola spreads to southeastern Uganda

News brief

Uganda's health ministry yesterday reported that Ebola has spread to Jinja district in the southeastern part of the country (see Google Maps image below).

On Twitter yesterday, the country's health minister Jane Ruth Aceng Ocero, MBChB, MPH, said the confirmed case in Jinja involves a 45-year-old man who died at his home on Nov 10 and was buried on Nov 12. Health workers from a clinic where he sought care earlier obtained a sample from the man on the day he died.Map of Jinja, Uganda

She said the man is a contact of a suspected case, his brother who traveled to Jinja where he was sick for 10 days and died on Nov 3. Ocero said the brother is listed as a suspected fatal case and is part of a cluster from Rubaga, which is in the Kampala area.

Ebola deaths that occur in community settings pose a high risk of further spread, because virus levels are typically at their highest when people are sickest and because contacts don’t typically have access to protective equipment.

Over the past few days, the country also reported another new case, involving a 17-year-old girl from Kassanda district, and another death in an earlier confirmed patient in Mubende district.

The outbreak total as of Nov 12 is 139 confirmed cases, 55 of them fatal, from nine districts, according to an update posted on the World Health Organization (WHO) Uganda office website. Also, there are least 21 suspected cases, all of them fatal. The outbreak, which began in September, involves the less common Sudan Ebola strain.

Study highlights COVID-related missed, delayed TB diagnosis

News brief

A study today in BMC Medicine highlights the toll that the COVID-19 pandemic has taken on the diagnosis of tuberculosis (TB) in high-burden countries, particularly in vulnerable populations.

To assess the impact of the pandemic on TB services, members of the TB Modelling Group at the London School of Hygiene & Tropical Medicine (LSHTM) modeled trends in age- and sex-disaggregated case notifications for all forms of new and relapse TB reported to the World Health Organization for 45 high TB, TB/HIV, and multidrug-resistant (MDR)-TB burden countries from 2013 through 2019. They then compared the trends predicted for 2020 with actual observed notifications that year and assessed disparities by age and sex.

Overall, more than 1.5 million people in the 45 countries were estimated to have had a missed or delayed TB diagnosis in 2020 because of COVID-19 disruptions, including 195,449 children, 1,126,133 people aged 15 to 64 years, and 235,402 individuals aged 65 years or older.

While the study found no evidence globally that the risk of having a missed or delayed TB diagnosis in 2020 was different for children and adults (risk ratio [RR], 1.09; 95% confidence interval [CI], 0.41 to 2.91), the elderly and younger adults (RR, 1.40; 95% CI, 0.62 to 3.16), or men and women (RR, 0.59; 95% CI, 0.25 to 1.42), there was some evidence of disparities when broken down by country.

In over half of the countries (57.1%) analyzed, for example, children were at greater risk of a missed or delayed TB diagnosis, while in 70.1% of countries, those aged 65 or older had a greater risk. In 45% of countries, sex was predicted to be an influential factor.

The study authors say the findings could aid efforts to mitigate the effects of the pandemic on TB services.

"Population groups whose access to TB diagnosis was disproportionately affected by the COVID-19 pandemic should be prioritised in catch-up campaigns," study co-author Katherine Horton, PhD, MPH, said in an LHSTM press release.

"For example, in settings where children have missed diagnoses, school-based strategies may be useful, while gender-sensitive strategies should be implemented in settings where one sex has been relatively under-diagnosed."

High-path H5 avian flu strikes more poultry in several countries

News brief

Several countries, including many in Europe, have reported more highly pathogenic H5N1 avian influenza outbreaks in poultry, according to the latest updates from the World Organization for Animal Health (WOAH).

In Europe, Denmark, Moldova, and Germany were among the countries reporting more outbreaks in poultry. Denmark reported that the virus struck a turkey farm housing 33,600 birds in the eastern part of the country neare the Zealand city Slagelse. The event is the country's first involving poultry since February. Moldova's outbreak, its first since September, occurred in a backyard flock of 48 birds in Hirisei in the north central part of the country. Also, Germany reported the virus at a poultry farm in Hessen state in the central part of the country.

Elsewhere, India recently reported two H5N1 outbreaks in backyard ducks at two locations not far from each other in Kerala state in the south, which led to the loss of more than 18,000 birds.

In other high path avian flu developments, South Africa reported a H5N2 outbreak in poultry at a farm in KwaZulu Natal province on its eastern coast.

In US developments, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) reported more highly pathogenic avian influenza outbreaks in two states. North Dakota reported outbreaks in backyard birds in Mountrail and Ward countries, and Pennsylvania had two more outbreaks at commercial turkey farms in Lehigh County.

Omicron BA.2 tied to more symptoms and, rarely, brain swelling in kids

News brief

UK study suggests that Omicron BA.2 is tied to more symptoms and greater disruption in daily activities than BA.1, and Taiwanese researchers describe fatal cerebral edema in six children hospitalized for BA.2.

Imperial College London researchers tracked SARS-CoV-2 transmission and symptoms among 1,542,510 randomly selected English adults, including 17,448 COVID-19 patients, from May 1, 2020, to Mar 31, 2022.

A greater proportion of BA.2 patients (75.9%) reported at least one of 26 symptoms, compared with 70.0% of those with BA.1, 63.8% with Delta, 54.7% with Alpha, and 45.0% with the wild-type virus.

Patients with wild-type, Alpha, or Delta infections were at highest risk for loss of sense of smell (odds ratios [ORs], 49.7, 37.8, and 73.4, respectively) and taste (ORs, 35.9, 38.9, and 68.1, respectively), while those with BA.1 or BA.2 had higher odds of flu- and cold-like symptoms.

A total of 17.6% of BA.2-infected people said their symptoms had affected their ability to complete daily activities "a lot," compared with 10.7% with BA.1 and 10.5% with Delta infections.

"With restrictions lifted and routine testing limited in many countries, monitoring the changing symptom profiles associated with SARS-CoV-2 infection and effects on daily activities will become increasingly important," the authors wrote.

In Taiwan, researchers examined clinical records from six BA.2-infected children diagnosed as having acute fulminant cerebral edema (usually fatal, rapid-onset brain swelling) from Apr 13 to Jun 30, 2022.

All six initially had shock and significantly elevated inflammatory biomarkers, with five rapidly progressing to multi-organ failure and diffuse blood-vessel clotting and three developing acute respiratory distress.

The researchers said that fever above 41oC (105.8oF) and atypical complex fever-related seizures are early signs of cerebral edema in pediatric patients. "The rapid and fulminant course highlights a need for close monitoring of cardiopulmonary and hematological functions in such patients, especially during the first day after the onset of neurological signs," they wrote.

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