Evaluation of rsv frequency in acute bronchiolitis by different methods

Abstract

Aim: Etiological and epidemiological studies of respiratory syncytial virus (RSV) infections in our country are not abundant. The aim of this study was to determine the frequency and general epidemiological properties of RSV in acute bronchiolitis (AB) and to investigate the accuracy and cost-effectivity of various diagnostic methods.A total of 76 children younger than 2 years of age who had the diagnosis of AB in the outpatient clinic or the emergency room were included. The criteria for the clinical diagnosis of viral AB were wheezing and sibilant rhonchi following a nonspecific viral upper respiratory infection of a few days along with hyperaeration on the chest X-ray. Patients with evidence of bacterial infection were excluded.The nasopharyngeal secretions (NS) and sera of the patients were obtained and stored at -20 degrees C to be subsequently tested for RSV antigen (Test Pack?, Abbott) in the NS and anti-RSV-IgG (two samples 14 days apart) as well as anti-RSV IgM antibodies in sera (ELISA, Euroimmune?). The assays were run simultaneously on the same batch.Of the 76 patients with AB, 73.6% were male and 26.4% were female. Their mean age was 9.4 +/- 5.3 months (X +/- SD; range: 2-24). The age distribution was 2-6 months in 26.3% patients, 7-12 months in 52.6% patients, and 13-24 months in 21.1% patients.RSV antigen in NS was positive in 36 (47.3%) patients, 4 of whom (5.2%) had anti-RSV-IgM in sera as well. Anti-RSV IgM was detected in an additional 3 patients whose NS were antigen-negative adding up to 39 (51.2%) patients with AB. Four patients tested positive for anti-RSV IgM only one of whom had a positive antigen in the NS. Out of 16 patients who had anti-RSV IgG concentration and were assayed twice after 14 days, 2 (12.5%) patients had increased concentrations of anti-RSV IgG in the second sample.Male/female ratio was 31/8 in RSV positive patients, and 25/12 in RSV negative patients (p>0.05). The age of patients with and without RSV was not significantly different (p>0.05). Seventy out of 76 (92%) patients presented between October and April. The month of presentation between the RSV positive and negative patients was not different (p>0.05). Forty-two (55%) patients were hospitalized and 34 (45%) were treated as outpatients. The cost of antibiotics and diagnostic tests were calculated for each patient.The cost of antibiotics was 45+30 USD in RSV positive patients, and 90.5+90.5USD in RSV negative patients. One test for RSV antigen cost similar to 13.3 USD, anti RSV IgM 4.58 USD, and anti-RSV IgG (two assays) 6.6 USD. The total cost even when all tests were done on one patient was less expensive than an unnecessary antibiotic treatment.RSV was detected in approximately half of the patients with AB. When compared to fast RSV antigen detection by EIA, serologic tests (ELISA IgM and IgG) had a high frequency of false negativity. Antigen detection in NS should be the preferred method for the diagnosis of RSV in AB which is highly cost-effective especially during the epidemic months.