Faculty Collaboration Database

Distribution of SARS-CoV-2 PCR Cycle Threshold Values Provide Practical Insight Into Overall and Target-Specific Sensitivity Among Symptomatic Patients. Am J Clin Pathol 2020 Sep 08;154(4):479-485

Date

07/21/2020

Pubmed ID

32687186

Pubmed Central ID

PMC7454307

DOI

10.1093/ajcp/aqaa133

Scopus ID

2-s2.0-85091263722 (requires institutional sign-in at Scopus site)   47 Citations

Abstract

OBJECTIVES: We examined the distribution of reverse transcription polymerase chain reaction (RT-PCR) cycle threshold (CT) values obtained from symptomatic patients being evaluated for coronavirus disease 2019 (COVID-19) to determine the proportion of specimens containing a viral load near the assay limit of detection (LoD) to gain practical insight to the risk of false-negative results. We also examined the relationship between CT value and patient age to determine any age-dependent difference in viral load or test sensitivity.

METHODS: We collected CT values obtained from the cobas severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) assay corresponding to 1,213 combined nasopharyngeal-oropharyngeal specimens obtained from symptomatic individuals that were reported as positive or presumptive positive for SARS-CoV-2. CT values were stratified by SARS-CoV target and patient age group.

RESULTS: In total, 93.3% to 98.4% of specimens demonstrated CT values greater than 3× the assay LoD, at which point false-negative results would not be expected. The mean of CT values between age groups was statistically equivalent with the exception of patients in age group 80 to 89 years, which demonstrated slightly lower CTs.

CONCLUSIONS: Based on the distribution of observed CT values, including the small proportion of specimens with values near the assay LoD, there is a low risk of false-negative RT-PCR results in combined nasopharyngeal-oropharyngeal specimens obtained from symptomatic individuals.

Author List

Buchan BW, Hoff JS, Gmehlin CG, Perez A, Faron ML, Munoz-Price LS, Ledeboer NA

Authors

Blake W. Buchan PhD Professor in the Pathology department at Medical College of Wisconsin
Jessica Hoff PhD Assistant Professor in the Pathology department at Medical College of Wisconsin
Nathan A. Ledeboer PhD Vice Chair, Professor in the Pathology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adolescent
Adult
Age Factors
Aged
Aged, 80 and over
Betacoronavirus
Child
Child, Preschool
Clinical Laboratory Techniques
Coronavirus Infections
False Negative Reactions
Female
Humans
Infant
Infant, Newborn
Limit of Detection
Male
Middle Aged
Pandemics
Pneumonia, Viral
RNA, Viral
Reverse Transcriptase Polymerase Chain Reaction
Sensitivity and Specificity
Viral Load
Wisconsin
Young Adult