RESUMEN
BACKGROUND: Lower respiratory tract infection by respiratory syncytial virus (RSV) is the most frequent cause of admission in children under 2 years old. The RSV subgroups A and B may circulate simultaneously. We aimed to determine whether clinical differences exist between RSV subgroups A and B. Additionally, we tested the sensitivity of the rapid antigen detection test (RADT) based on immunochromatography in diagnosing subgroups A and B, taking the polymerase chain reaction assay (RT-PCR) as reference. METHODS: A retrospective observational study was performed in a tertiary hospital from October 2013 to March 2014. Clinical records and analytical variables of all children under 5 admitted with lower respiratory tract infection and RT-PCR positive for RSV in nasal lavage were consulted. Previously, the RADT for RSV had been performed from the same sample. RESULTS: A total of 198 children under 5 were diagnosed with RSV by RT-PCR: 55 (28%) were RSV-A, 132 (67%) RSV-B and 11 (5%) were positive for both subgroups. No differences were observed between subgroups in medical history, symptoms, radiological and analytical findings, and severity. The sensitivity of RADT for RSV was 52%, higher for RSV-A (69%) than for RSV-B (44%, p=0.001). CONCLUSIONS: The two RSV subgroups were indistinguishable in symptoms and prognosis. The sensitivity of RADT compared to RT-PCR was low and limits its usefulness for clinical decision-making. Key words. Respiratory syncytial virus. RSV subgroups. Rapid antigen detection test. Reverse transcription polymerase chain reaction.