The diagnosis of acute otitis media (AOM) is often difficult, depending heavily on the experience and skills of the examiner. However, it is important to identify episodes of AOM that involve the risk of complications and to treat these episodes appropriately. The present study was performed in order to evaluate the use of a rapid antigen assay for Streptococcus pneumoniae, the Binax NOW test, as a diagnostic tool in patients with severe AOM and associated complications. The study included 70 patients with 74 episodes of AOM, 18 of them with complications. Cultures, Binax NOW tests, and a PCR assay were performed on nasopharyngeal secretions, middle ear fluid, and in some cases mastoid bone, cerebrospinal fluid, and urine. According to culture and PCR of the middle ear fluid, 30 (41%) of the episodes were caused by S. pneumoniae. The Binax NOW test was positive in 24 of these episodes (80%). It identified pneumococcal AOM independent of antibiotic treatment, and it was easily adapted to bone tissue. The test yielded sensitivity, specificity, and positive and negative predictive values for middle ear specimens of 85%, 100%, 100%, and 89%, respectively. The corresponding positive and negative values for predicting the bacterial etiology with nasopharyngeal secretions were 51% and 75%. This study showed that the Binax NOW test is a useful diagnostic tool for patients with severe AOM with or without complications.Acute purulent otitis media (AOM) is the most common bacterial infection diagnosed among children. By 3 years of age, up to 85% of all children have experienced at least one episode of AOM (40), and 15 to 20% of the children suffer from recurrent episodes (1, 7).The most frequent microbiological cause of AOM is Streptococcus pneumoniae (26 to 48%), followed by Haemophilus influenzae (15 to 41%), Moraxella catarrhalis (23 to 25%), and Streptococcus pyogenes (4 to 8%) (2,3,20,27). S. pneumoniae and S. pyogenes are the two most virulent pathogens of the middle ear, and they are the leading causes of complications such as mastoiditis, labyrinthitis, and meningitis (15,22,23,28,38).AOM is the single most common reason for prescribing antibiotics to children (12, 24). The antibiotic load and selective pressure in the youngest age groups are consequently high, and clinical problems with antibiotic resistance have emerged (5, 41). The routine use of antimicrobial drugs in AOM treatment has been reevaluated in recent years, and watchful waiting has become an alternative (34). Watchful waiting is, however, not without risk. A safer approach is to use stricter diagnostic criteria for AOM, to improve the diagnostic tools, and to treat only those patients who are the least likely to recover spontaneously.The diagnosis of AOM, especially in young children, is often difficult and inadequate (4,12,33,42). Previous studies have shown that physicians are uncertain of the diagnosis in 40% of cases (31), and general practitioners are more likely to diagnose AOM than are otorhinolaryngologists (4). Furthermore, about 49 to 88% ...