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MCQ – 88949

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Question

It is winter,  when a 3-year-old previously healthy child is brought to the emergency department after the parents witness a 5- to 10- minute episode of shaking of the arms and legs. The shaking stopped while on route to the emergency department. The child is now sleepy and not responsive to questions but responds during the exam. His temperature is 103.1 F. There is minimal nasal congestion, the throat is erythematous, the neck is supple, and bilateral anterior cervical adenopathy is present. The spleen tip is palpable. Heart exam is normal, and lungs are clear. What is a rapid and sensitive method to make the diagnosis?
A. Viral culture of nasopharyngeal specimen
B.

Influenza A enzyme immunoassay antigen detection on throat specimen
C.

Influenza A direct fluorescent antibody on nasopharyngeal specimen
D.

Influenza A IgG serology on acute serum
Show Answer

Correct Answer � C

Explanation

Ans: C, Influenza A direct fluorescent antibody on nasopharyngeal specimen

The rapid antigen tests commercially available for identification of influenza A or B have variable sensitivity and specificity compared to viral culture.

The direct fluorescent antibody is more sensitive than the rapid antigen tests, and its sensitivity is high (90%) when compared with culture.

Serologic testing with acute and convalescent serum can identify children with influenza not detected by other methods but is not helpful for rapid diagnosis. According to the Centers for Disease Control and Prevention, “During periods when influenza activity is high and influenza viruses are circulating among persons in the community, the positive predictive value of a test result is high”

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