We use cookies to understand how you use our site and to improve your experience. This includes personalizing content and advertising. To learn more, click here. By continuing to use our site, you accept our use of cookies. Cookie Policy.

Features Partner Sites Information LinkXpress hp
Sign In
Advertise with Us

Download Mobile App





WHO Changes SARS-CoV-2 Virus Test Criteria to Reduce False Positives

By LabMedica International staff writers
Posted on 25 Jan 2021
In its updated guidance, the World Health Organization (WHO; Geneva, Switzerland) has cautioned experts not to rely solely on the results of a PCR test to detect the SARS-CoV-2 virus and consider the results in combination with other factors such as timing of sampling, specimen type, and assay specifics, among others.

The WHO has updated its guidance on nucleic acid testing (NAT) technologies that use polymerase chain reaction (PCR) for the detection of SARS-CoV-2. More...
It has requested users to follow the instructions for use (IFU) when interpreting results for specimens tested using PCR methodology. The WHO has advised users of IVDs to read and follow the IFU carefully to determine if manual adjustment of the PCR positivity threshold is recommended by the manufacturer.

According to the WHO’s guidance on diagnostic testing for SARS-CoV-2, careful interpretation of weak positive results is needed as the cycle threshold (Ct) needed to detect the virus is inversely proportional to the patient’s viral load. Where test results do not correspond with the clinical presentation, it recommends that a new specimen should be taken and retested using the same or different NAT technology.

The WHO has reminded IVD users that disease prevalence alters the predictive value of test results; as disease prevalence decreases, the risk of false positive increases. This means that the probability that a person who has a positive result (SARS-CoV-2 detected) is truly infected with SARS-CoV-2 decreases as prevalence decreases, irrespective of the claimed specificity. Since most PCR assays are indicated as an aid for diagnosis, the WHO has advised health care providers to consider any results in combination with the timing of sampling, specimen type, assay specifics, clinical observations, patient history, confirmed status of any contacts, and epidemiological information.

Related Links:
World Health Organization (WHO)


Gold Member
SARS‑CoV‑2/Flu A/Flu B/RSV Sample-To-Answer Test
SARS‑CoV‑2/Flu A/Flu B/RSV Cartridge (CE-IVD)
Portable Electronic Pipette
Mini 96
New
Sperm Quality Analyis Kit
QwikCheck Beads Precision and Linearity Kit
New
Clinical Chemistry System
P780
Read the full article by registering today, it's FREE! It's Free!
Register now for FREE to LabMedica.com and get access to news and events that shape the world of Clinical Laboratory Medicine.
  • Free digital version edition of LabMedica International sent by email on regular basis
  • Free print version of LabMedica International magazine (available only outside USA and Canada).
  • Free and unlimited access to back issues of LabMedica International in digital format
  • Free LabMedica International Newsletter sent every week containing the latest news
  • Free breaking news sent via email
  • Free access to Events Calendar
  • Free access to LinkXpress new product services
  • REGISTRATION IS FREE AND EASY!
Click here to Register








Channels

Clinical Chemistry

view channel
Image: The study highlights the potential of cCAFs as a biomarker for early diagnosis and prognosis (H J Woo et al., Analytical Chemistry (2025). DOI: 10.1021/acs.analchem.5c02154)

Simultaneous Cell Isolation Technology Improves Cancer Diagnostic Accuracy

Accurate cancer diagnosis remains a challenge, as liquid biopsy techniques often fail to capture the complexity of tumor biology. Traditional systems for isolating circulating tumor cells (CTCs) vary in... Read more

Hematology

view channel
Image: New research points to protecting blood during radiation therapy (Photo courtesy of 123RF)

Pioneering Model Measures Radiation Exposure in Blood for Precise Cancer Treatments

Scientists have long focused on protecting organs near tumors during radiotherapy, but blood — a vital, circulating tissue — has largely been excluded from dose calculations. Each blood cell passing through... Read more

Immunology

view channel
Image: The VENTANA HER2 (4B5) test is now CE-IVDR approved (Photo courtesy of Roche)

Companion Diagnostic Test Identifies HER2-Ultralow Breast Cancer and Biliary Tract Cancer Patients

Breast cancer is the most common cancer in Europe, with more than 564,000 new cases and 145,000 deaths annually. Metastatic breast cancer is rising in younger populations and remains the leading cause... Read more

Technology

view channel
Image: Conceptual design of the CORAL capsule for microbial sampling in the small intestine (H. Mohammed et al., Device (2025). DOI: 10.1016/j.device.2025.100904)

Coral-Inspired Capsule Samples Hidden Bacteria from Small Intestine

The gut microbiome has been linked to conditions ranging from immune disorders to mental health, yet conventional stool tests often fail to capture bacterial populations in the small intestine.... Read more
Copyright © 2000-2025 Globetech Media. All rights reserved.