Validity of Immunofluorescence Test for the Detection of Respiratory Viruses Causing Acute Lower Respiratory Tract Infection Among Under Five Children

Background: Respiratory viruses cause a variety of human infections, ranging from the common cold to life-threatening pneumonia. Over 200 strains of virus can cause respiratory disease. The majority of severe viral respiratory infections are caused by relatively few viruses, primarily parainfluenza virus types 1, 2 and 3, respiratory syncytial virus (RSV), influenza A and B viruses, and adenovirus. Objective: The purpose of this study was to see the validity of Immunofluorescence test for the detection of Respiratory viruses causing acute lower respiratory tract infection among under five children. Methodology: This cross sectional study was conducted in the Department of Virology at Bangabandhu Sheikh Mujib Medical University, Dhaka from July 2002 to June 2003 for a period of one year. The children with the age group of below five (5) years presented with the clinical manifestations of acute lower respiratory tract infection (ALRI) who were visited or were admitted to Dhaka Medical College Hospital (DMCH), Dhaka were selected as study population. Nasopharyngeal aspirates were collected. Viruses were detected by cell line culture and direct Immunoflorescence (DFA) method. Result: The study was carried out among 100 children aged from new born to 60 months with acute lower respiratory tract infection (ALRI). Highest rate (85.7%) of isolation was obtained among children between 0 to 24 months of age. There was a significant reduction in the number of cases in older children in 25 to 60 months of age group. The most common virus isolated from the under five children was respiratory syncytial virus which was 20(95.2%). Adenovirus was isolated in only 1(4.8%) case. No other viruses were found in this study. DFA method typically more rapid than the cell culture and also detect virus which has lost viability in transit. Culture methods on the other hand, are more favorable for detecting low titer of viable virus. In this study 17 samples are positive by cell culture and these are also positive by DFA. Total 21 samples are positive by DFA and among them 4 samples are negative. Conclusion: DFA is highly sensitive and specific for detection of respiratory viruses among the under-five children. Furthermore the accuracy of this test is also very high. Therefore it is recommended that the DFA test can be used for the detection of respiratory virus from the children presented with respiratory tract infection.