Rickettsial Disease Diagnostic Testing and Interpretation

This video provides information on rickettsial disease diagnostic methods for healthcare providers, including what tests are available and when it is most appropriate to collect samples. This video focuses on the use of polymerase chain reaction (or PCR) tests, and the indirect immunofluorescence antibody (IFA) assay for rickettsial disease diagnosis.

Author/s:

Centers for Disease Control and Prevention

Dynamics and Correlation Among Viral Positivity, Seroconversion, and Disease Severity in COVID-19

Devin Evans — Mon, 21 Dec 2020 06:00:00 +0000

Date Added:

December 21, 2020

Journal/Publication:

Annals of Internal Medicine

Publication Date:

December 8, 2020

URL:

Dynamics and Correlation Among Viral Positivity, Seroconversion, and Disease Severity in COVID-19

Type:

Clinical Research Results

Format:

Article

DOI (1):

10.7326/M20-3337

Keywords

COVID-19

coronavirus

SARS coronavirus

Polymerase chain reaction

PCR

PMID (1):

33284684

MeSH

Reverse Transcriptase Polymerase Chain Reaction

COVID-19

Coronavirus

Critical Illness

The figures in this article show the course of PCR positivity and appearance of antibodies during the course of confirmed COVID-10 cases. The information should be helpful when deciding when to order those tests and how to interpret the results. James W. Mold, MD, MPH

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Background: The understanding of viral positivity and seroconversion during the course of coronavirus disease 2019 (COVID-19) is limited.

Objective: To describe patterns of viral polymerase chain reaction (PCR) positivity and evaluate their correlations with seroconversion and disease severity.

Design: Retrospective cohort study.

Setting: 3 designated specialty care centers for COVID-19 in Wuhan, China.

Participants: 3192 adult patients with COVID-19.

Measurements: Demographic, clinical, and laboratory data.

Results: Among 12 780 reverse transcriptase PCR tests for severe acute respiratory syndrome coronavirus 2 that were done, 24.0% had positive results. In 2142 patients with laboratory-confirmed COVID-19, the viral positivity rate peaked within the first 3 days. The median duration of viral positivity was 24.0 days (95% CI, 18.9 to 29.1 days) in critically ill patients and 18.0 days (CI, 16.8 to 19.1 days) in noncritically ill patients. Being critically ill was an independent risk factor for longer viral positivity (hazard ratio, 0.700 [CI, 0.595 to 0.824]; P < 0.001). In patients with laboratory-confirmed COVID-19, the IgM-positive rate was 19.3% in the first week, peaked in the fifth week (81.5%), and then decreased steadily to around 55% within 9 to 10 weeks. The IgG-positive rate was 44.6% in the first week, reached 93.3% in the fourth week, and then remained high. Similar antibody responses were seen in clinically diagnosed cases. Serum inflammatory markers remained higher in critically ill patients. Among noncritically ill patients, a higher proportion of those with persistent viral positivity had low IgM titers (<100 AU/mL) during the entire course compared with those with short viral positivity.

Limitation: Retrospective study and irregular viral and serology testing.

Conclusion: The rate of viral PCR positivity peaked within the initial few days. Seroconversion rates peaked within 4 to 5 weeks. Dynamic laboratory index changes corresponded well to clinical signs, the recovery process, and disease severity. Low IgM titers (<100 AU/mL) are an independent risk factor for persistent viral positivity.

Author/s:

Fu, Yu, Li, Yongsheng, Guo, Ensong, He, Liang, Liu, Jia, Yang, Bin, Li, Fuxia, Wang, Zizhuo, Li, Yuan, Xiao, Rourou, Liu, Chen, Huang, Yuhan, Wu, Xue, Lu, Funian, You, Lixin, Qin, Tianyu, Wang, Chaolong, Li, Kezhen, Wu, Peng, Ma, Ding, Sun, Chaoyang, Chen, Gang