Concept of cycle threshold values in SARS-CoV-2 positive patients at
childbirth admission: a retrospective observational study
Abstract
Objective To evaluate relationships between cycle threshold values and
COVID-19 presentations and clinical courses in women presenting for
childbirth. Cycle threshold values from polymerase chain reaction (PCR)
testing are inversely proportional to viral burden and may be important
predictors of disease state and infectivity risk. Design Retrospective
cohort study Setting Three Yale-New Haven Health Hospitals between
4/2/2020-5/14/2020 Population Women presenting for childbirth who
underwent SARS-CoV-2 PCR testing Methods Electronic health records were
reviewed for socio-demographics, medical comorbidities, pregnancy and
postpartum course, and COVID-19 symptoms and exposures. Records of
SARS-CoV-2 positive women were reviewed for symptom onset, duration, and
relation to test timing, disease course, and neonatal SARS-CoV-2
results. Main Outcome Measures SARS-CoV-2 real-time PCR cycle threshold
values from positive tests were compared between asymptomatic and
symptomatic women and in relation to disease severity. In women with
symptomatic COVID-19, cycle threshold values were evaluated as a
function of time since symptom onset. Results 1,210 women gave birth
during the study period with 84 (6.9%) positive for SARS-CoV-2. Higher
cycle threshold values were seen in asymptomatic SARS-CoV-2 positive
patients (8/38 (21.1%) of asymptomatic women had cycle threshold
<30 compared to 22/32 (68.0%) of symptomatic women,
p<0.0001). In symptomatic women, values increased as time from
symptom onset increased. Conclusion This study demonstrates higher cycle
threshold values in asymptomatic patients and symptomatic patients
tested remote from symptom onset, signifying older infections and
detection of lower levels of viral RNA. Assessment of standardized cycle
threshold values may help to understand disease characteristics and
progression.