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Association of the C T values of real‐time PCR of viral upper respiratory tract infection with clinical severity, Kenya
Author(s) -
Fuller James A.,
Njenga M. Kariuki,
Bigogo Godfrey,
Aura Barrack,
Ope Maurice O.,
Nderitu Leonard,
Wakhule Lilian,
Erdman Dean D.,
Breiman Robert F.,
Feikin Daniel R.
Publication year - 2013
Publication title -
journal of medical virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 121
eISSN - 1096-9071
pISSN - 0146-6615
DOI - 10.1002/jmv.23455
Subject(s) - medicine , coinfection , asymptomatic , respiratory tract , respiratory system , logistic regression , human metapneumovirus , respiratory tract infections , viral load , virus , gastroenterology , virology , immunology
Quantitative real‐time polymerase chain reaction (qRT‐PCR) assay of the upper respiratory tract is used increasingly to diagnose lower respiratory tract infections. The cycle threshold (C T ) values of qRT‐PCR are continuous, semi‐quantitative measurements of viral load, although interpretation of diagnostic qRT‐PCR results are often categorized as positive, indeterminate, or negative, obscuring potentially useful clinical interpretation of C T values. From 2008 to 2010, naso/oropharyngeal swabs were collected from outpatients with influenza‐like illness, inpatients with severe respiratory illness, and asymptomatic controls in rural Kenya. C T values of positive specimens (i.e., C T values < 40.0) were compared by clinical severity category for five viruses using Mann–Whitney U ‐test and logistic regression. Among children <5 years old we tested with respiratory syncytial virus (RSV), inpatients had lower median C T values (27.2) than controls (35.8, P = 0.008) and outpatients (34.7, P < 0.001). Among children and older patients infected with influenza virus, outpatients had the lowest median C T values (29.8 and 24.1, respectively) compared with controls ( P = 0.193 for children, P < 0.001 for older participants) and inpatients ( P = 0.009 for children, P < 0.001 for older participants). All differences remained significant in logistic regression when controlling for age, days since onset, and coinfection. C T values were similar for adenovirus, human metapneumovirus, and parainfluenza virus in all severity groups. In conclusion, the C T values from the qRT‐PCR of upper respiratory tract specimens were associated with clinical severity for some respiratory viruses. J. Med. Virol. 85:924–932, 2013. © 2013 Wiley Periodicals, Inc.