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CMAAO Coronavirus Facts And Myth Busters: Lab errors with new strain

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Dr KK Aggarwal    10 January 2021

With input from Dr Monica Vasudev

1295: In hospitalized COVID-19 patients with no previous neurologic disease, 37.4% were found to have abnormalities on neurologic exam 6 months later, most common being cognitive deficits, hyposmia, and postural tremor, reported researchers in a medRxiv preprint that has not undergone peer review.

Patients also noted fatigue, memory impairment, and sleep disorders. The severity of SARS-CoV-2 infection was a key predictor, along with age and premorbid condition, of long-term neurological symptoms and features in the cohort.

Earlier research had revealed that 87% of patients hospitalized with COVID-19 reported persistence of at least one lingering symptom, particularly fatigue and dyspnea, 60 days following discharge. Fatigue and dyspnea also were the most prevalent symptoms reported during infection and at 3-month follow-up in an analysis of both hospitalized and non-hospitalized patients.

The checklist including symptoms related to central, peripheral, myopathic, and cognitive manifestations. The evaluation assessed cranial nerves; motor, sensory, cerebellar, and basal ganglia-related function; deep tendon reflexes; pyramidal signs; and global cognitive function using the Montreal Cognitive Assessment (MoCA).

Among 165 patients, the most common symptoms at follow-up included fatigue (34.1%), memory complaints (30.8%), sleep disorders (30.8%), myalgias (29.6%), depression or anxiety symptoms (26.0%), blurring or other visual disturbances (19.5%), paresthesia (18.3%), and hyposmia/dysgeusia (16.5%).

Additionally, around14.0% patients reported urinary dysfunction, 13.0% had confusion/dizziness, 12.2% had dizziness/hypotension, 10.7% had gait disturbances, and 8.5% had postural instability or falls.

In all, 105 patients were evaluated further by neurologic exam and cognitive screening. Forty two of these showed neurologic abnormalities: 19 had hyposmia/dysgeusia, 15 had enhanced physiological tremor, 6 had low-limb hypoesthesia, 3 had low-limb motor deficits, and 17 had cognitive deficits, as per MoCA Italian validated norms. None of these patients had a history of cognitive impairment.

Neurologic abnormalities noted on examination were associated with older age (P=0.005), higher premorbid comorbidity index (P=0.001), worse BCRSS scores (P=0.05), longer hospitalization duration (P=0.002), and higher number of neurologic symptoms reported (P=0.007). Length of hospitalization (P=0.02) and premorbid comorbidity index (P=0.03) were predictors of neurologic abnormalities.

Cognitive impairment was linked with severity of COVID-19, independent of age and pre-morbid conditions. (Medpage Today)

1296: Results from Pfizer/BioNTechs late-stage clinical trial suggest that one dose of the vaccine might confer some level of immunity, with an efficacy rate of around 52%. However, the one-dose regimen has not received any government approval, as vaccine efficacy shoots to 95% after the second dose. (Medpage Today)

1297: A small number of asymptomatic close contacts of COVID-19 cases ultimately tested positive after an initial negative test followed by quarantining for 7 days, noted Vermont health officials.

Among 977 asymptomatic contacts of COVID-19 cases from May to November, 34 (3%) tested positive for COVID-19 after the week-long quarantine, reported Veronica Fialkowski, MPH, of the Vermont Department of Health in Burlington, and colleagues, in the CDCs Morbidity and Mortality Weekly Report. (Medpage Today)

1298: US regulators have warned about the potential risk for false negative results with molecular tests for SARS-CoV-2 owing to mutations such as a recently detected B.1.1.7 variant of the virus.

The US FDA warned that false negative results can occur with any molecular test for the detection of SARS-CoV-2 if a mutation occurs in the part of the virus genome assessed by that particular test. The risk that these mutations will affect overall testing accuracy appears to be low.

Like all viruses, SARS-CoV-2 was expected to mutate over time, as seen with the emergence of the B.1.1.7 variant, stated the FDA.

In a letter to healthcare workers, the FDA stated on Friday that its analysis to date has identified three molecular tests that have received emergency use authorization (EUA) whose performance could be impacted by SARS-CoV-2 genetic variants.

  1. Accula SARS-CoV-2 Test: The FDAs analysis indicates that this tests performance may be affected when a SARS-CoV-2 virus patient’s sample with a genetic variant at position 28881 (GGG to AAC) is tested. While the impact does notseem to be significant, the FDA is providing this alert.
  2. TaqPath COVID-19 Combo Kit and Linea COVID-19 Assay Kit: The detection pattern that appears with these diagnostic tests when certain genetic variants are present may help with early identification of new variants to reduce further spread of infection.
  3. The FDA also advised healthcare professionals to be aware of the pattern of detection associated with certain mutations, including the B.1.1.7 variant, particularly a pattern of 2/3 positive targets showing the S-gene dropout (reduced sensitivity with the S-gene target), when using the TaqPath COVID-19 Combo Kit, and a pattern of 1/2 positive targets showing the S-gene dropout while using the Linea COVID-19 Assay Kit.

Recommendations for clinical laboratory staff and clinicians using molecular tests for the detection of SARS-CoV-2:

  1. Be aware that genetic variants of SARS-CoV-2 arise regularly, and false negative test results can occur
  2. Be aware that tests that use multiple genetic targets to ascertain a final result will less likely be affected by increased prevalence of genetic variants

iii.     Consider negative results in association with clinical observations, patient history, and epidemiological information

  1. Repeat testing to be considered with a different test (with different genetic targets) if COVID-19 is still suspected after receiving a negative test result

In South Africa, another variant, known as 20C/501Y.V2 or B.1.351 lineage, has emerged independently of the B.1.1.7 lineage. This variant shares some mutations with the B.1.1.7 lineage. According to the CDC, cases attributed to this variant have been detected outside of South Africa. (Medscape)

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA

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