Evaluation of nucleic acid amplification assay and rapid antigen assay of nasopharynx swabs and oropharynx swabs from flu-like patients in diagnosis of flu A / 中华传染病杂志

ABSTRACT

Objective To compare the detection of flu A by nucleic acid amplification assav and rapid antigen assay in nasopharynx swabs and oropharynx swabs of flu-like patients.Methods A total of 170 flu-like patients were recruited in out-patient of Youan Hospital from September to October in 2009.Both nasopharynx swabs and oropharynx swabs were collected.Flu A virus was detected by both real-time reverse transcriptation polymerase chain reaction (RT-PCR) and rapid antigen assay.The data were analyzed by chi square test.Results For nasopharynx swabs,the positive rate of nucleic acid amplification assay was 74.1%(126/170),while that of rapid antigen assay was 65.9%(112/170)(X2=2.75,P>0.05).However,for oropharynx swabs,the positive rate of nucleic acid amplification assay was much higher than that of rapid antigen assay(62.9% vs 38.8%)(X2=19.78,P<0.01).Moreover,for nucleic acid amplification assay,the positive rate of nasopharynx swabs were higher than that of oropharynx swabs (X2=4. 90, P<0. 05). For rapid antigen assay, the positive rate of nasopharynx swabs was also higher than that of oropharynx swabs (X2=24.95, P<0.01). Based on the outcome of flu A detected with nasopharynx swabs by the nucleic acid amplification assay,the sensitivities of oropharynx swabs by nucleic acid amplification assay,oropharynx swabs by rapid antigen assay, nasopharynx swabs by rapid antigen assay were 81.7%,50.0% and 94.8%, respectively; the specifieities were 90.9%, 93.2% and 95.5%, respectively;the positive predictive values were 96. 3%, 95. 5% and 98.2%, respectively; the negative predictive values were 63.5 %, 39.4 % and 72.40%, respectively; Kappa coefficients were 0.64, 0.30 and 0.75,respectively; the total coincidences were 84.1%, 61.20% and 89.4%, respectively. Conclusions The detection of flu A with nasopharynx swabs is more sensitive than oropharynx swabs, and nucleic acid amplification assay is more sensitive than rapid antigen assay.