Establishment Of Gold Immunchromatographic Assay On Rapid Detecting Antigen Of Influenza Virus And Its Application

Background Influenza (Flu)is an acute infectious disease caused by influenza virus. It characters as strong infectivity, rapid and wide spread. The diagnosis of influenza based on not only the clinical symptoms and signs, but also laboratory tests to confirm. At present, the commonly used detection methods of influenza virus includes mainly virus isolation and culture, the enzyme immunoassay, immunofluorescence and PCR technique. Virus isolation and culture are the gold standard for diagnosis of influenza. As the process often requires 2-14 days, it is not very helpful to early diagnosis of influenza. Indirect immunofluorescence assay(IFA) to detect the virus antigen is fast and accurate, IFA method because of its stable, sensitive and specific advantages , is used widely. But the disadvantages is the need of expensive immunofluorescence microscopy and experienced staff . Immunity colloidal gold technique is simple, fast, accurate and non-polluting, it provides an excellent technology platform to set up a method for rapid detection of antigen of influenza virus.Objective To set up an effective and simple method, GICA, for rapid detection of influenza virus infection. For rapid detection of antigen of influenza virus in patients with respiratory infections, the method was used to analyze of the rules and characteristics of infection of the influenza virus.Methods1. 1042 patients with different types respiratory diseases during Feb 2007 to Jan 2009 were selected for check. GICA assay was used to detect influenza virus A/B (FluA/ B) antigen in nasopharyngeal secretions of patients and in the meanwhile, by comparing with IFA, for verifing sensitivity and specificity of GICA method . 60 cases of positive samples and 10 cases of negative samples of influenza virus antigen was detected by GICA for virus isolation and culture at the same time, which further confirmed the reliability of GICA.2. Nasopharyngeal secretions from patients were collected by the methods of nasopharynx swab or nasopharyngeal suction catheter. Both methods were applied with GICA kit to detect rapidly FluA/B antigen in secretion specimens, then the evaluation to the results of different collection methods was made.3. To analyze the result of Flu A/B antigen deteced by GICA for 1042 patients with various types of respiratory diseases. Influenza virus detection rates of patients in different seasons , and with different gender, age, types of respiratory diseases and whether with foundation diseases were analyzed to identify the common rules and characteristics.Results1.It shows good consistency of the results for detecting FluA/B with GICA method and IFA method. The two mthods were dependent. The difference between the GICA and the IFA for the detection of influenza viruses had no statistical significance (P>0.05). It has high consistency of detection results to Flu A/B by using GICA and virus culture.2. Methods of collecting samples by using the nasopharynx swab and nasopharyngeal suction catheter for rapid detection of Flu A/ B shows good consistency. The difference between the two methods had no statistical significance (P> 0.05).3. Flu A/B detection rate in the first and the fourth quarter compared with the second and third quarter, the results indicated differences between the two groups is significant; detection rate of the first and fourth quarter was higher than the sencod and third quarter. The difference of Flu A/ B positive detection rate between male group and female group is negative.The difference of Flu A/B positive detection rate in groups between≥65 years old and<65 years old has statistically significance. Older patients (≥65 years old) have higher Flu A/ B detection rate.The difference of Flu A/B detection rate of patients without foundation diseases and with one, two or three kinds of foundation diseases has statistical significance. It indicated, with an increase in the number of species of the founation diseases, Flu A/ B-positive detection rate increased.In patients with various diseases, the FluA antigen detection rate in group of AECOPD patients is 18.7% and pneumonia group is 17.4%, which are higher than that in the other diseases.Conclusions 1. The method of using GICA to detect rapidly Flu A/B antigen from nasopharyngeal secretions is simple, convenient and rapid. Its specificity and sensitivity, especially the specificity is good, and the results indicated that there are good appliance of GICA for clinical detection of Influenza viruses.2. Collecting nasopharyngeal secretions by nasopharynx swab for rapid detection of influenza virus is a more reliable, faster and more convenient, compared with collecting method by nasopharyngeal suction catheter .3. Sporadic cases of influenza were found in general wards, incidence rate is higher in the first and the fourth quarter. There is a higher risk of influenza virus infection for old-age patients and patients with foundation diseases. The FluA detection rates for AECOPD and pneumonia patients are relatively higher.