Comparison of the quick view influenza test (Quidel) to an immunofluorescence assay for the detection of influenza virus infections.

The performancs of a membrane-based EIA, the Quick Vue Influenza test, (Quidel,USA) were compared to those of an immunofluorescence assay (IFA) for the detection of influenza virus A antigens in respiratory samples from children hospitalized during the 2002-2003 winter season. A prospective study was carried out on 2 nasal swabs drawn in parallel from 33 children: 13 samples were positive and 18 negative on both the Quick Vue test and IFA. Using an in-house reverse transcription (RT)- PCR assay as a gold standard, the two discordant results were identified as a false-positive reaction of the IFA and a false-negative one of the Quick Vue test . The sensitivity, specificity, positive and negative predictive values of the Quick Vue test were 87.5%, 100%, 100% and 89.5%, respectively. In the retrospective study of frozen samples, 57 of the 70 positive samples were detected by the Quick Vue test and 5 of 50 negative samples. Using the RT-PCR as a gold standard, there were 4 false-negative and 3 false-positive results on IFA and 10 false-negative results on the Quick Vue test. Our study suggests that performances of the Quick Vue are good if the test is carried out directly on nasal secretions, but that they can be decreased when nasal aspirates are collected in transport medium and frozen.

Viral etiology of acute respiratory infections in infants and young children.

114 children with acute respiratory infections were investigated to detect the viral etiological agents. The following methods were used: the direct immunofluorescence technique for the rapid diagnosis from tracheobronchial aspirates and the serological reactions--hemaglutinoinhibition and complement fixation reaction--to determine the increase of antibodies titres. Of 55.2% respiratory infections with a viral etiology, 60.3% represent acute infections of the lower respiratory tract. Due to the influenza epidemic reported between October 1996 and February 1997 (with a higher number of cases than in the last 5 years), most viral respiratory infections were caused by influenza viruses (57.14%). The direct immunofluorescence technique proved to be sensitive and specific in detecting the viral etiological agents which caused respiratory infections. Thus, using this technique, a positive diagnosis was made in 68.2% of cases, of which 49.2% were positive by the hemagglutination and complement fixation reactions, too. The test specificity could have been higher if the pathological products had been prelevated within the first three days after the onset of the disease.

[ELISA in the rapid diagnosis of influenza using as the detecting antibodies polyclonal antinucleoprotein sera]. / ELISA in diagnosticul rapid al gripei utilizând ca anticorpi detectori seruri policlonale antinucleoproteina.

Hyperimmune polyclonal sera were obtained in order to use them as capture and detecting antibodies in rapid diagnostic of influenza A and B viruses by ELISA. The test shown 100% specificity. The sensitivity in directly detection of influenza viruses in human samples compared of influenza isolations was 49,25% for type A and 53,33% for type B. The sensitivity was increased after 48 hours from inoculation of human samples in cell culture-86,75% for type A detection and 80,0% for type B detection from supernatant mammalian tissue culture (MDCK).

Seroepidemiological study of the circulation of influenza C virus in man.

The seroepidemiological study of the circulation of influenza C virus was achieved by testing HI antibodies in human sera collected from healthy subjects in Bucharest belonging to various age groups. The investigations were carried out over a two years period (October 1988--September 1990), using 3 influenza C virus strains: C/Taylor/1233/47, C/USSR/0303/77 and C/Moscow/1/84, the last two being antigenically similar. The analysis of the distribution of HI antibody values against the three influenza C virus strains showed that over October 1988--June 1989 the reported circulating viruses belonged to two distinct antigenic groups, one similar to the prototype C/Taylor/47 strains and the other to C/USSR/and/C/Moscow strains, whilst during the July 1989--September 1990 time interval viruses belonging solely to the C/USSR and C/Moscow antigenic group circulated. Similarly, one should note that circulation of influenza C viruses is not seasonal, it can appear anytime and even several times per year; this accounts for the relatively high and permanent antibody level in the population belonging to all age groups.