Clinical profile of serologically diagnosed pneumococcal pneumonia

Objective. To describe the characteristics of serologically diagnosed pneum ococcal pneumonia and compare them with those of respiratory syncytial viru s (RSV) pneumonia and bacteremic pneumococcal pneumonia. Methods. IgG antibodies to pneumococcal pneumolysin and C-polysaccharide as well as immune complexes containing IgG antibodies to pneumolysin and C-po lysaccharide were measured from acute and convalescent sera of 254 children with community-acquired pneumonia. Evidence of pneumococcal. infection was found in 93 children. Clinical and laboratory data were retrospectively co llected from the records of 38 children with sole (all tests for 16 other m icrobes negative) pneumococcal pneumonia and compared with 26 sole RSV-indu ced pneumonia from the present series and with the data of our 85 bacteremi c pneumococcal pneumonia cases reported earlier. Results. Serologically diagnosed sole pneumococcal pneumonia clinically ove rlapped with RSV pneumonia, but RSV pneumonia was more often associated wit h tachypnea (45% vs. 17%, P < 0.05) and low white blood cell counts (means, 12.0 x 10(9)/l vs. 20.8 x 10(9)/l; P < 0.001) as well as low serum C-react ive protein levels (means, 28 mg/l vs. 137 mg/l; P < 0.001). Alveolar infil trates were found in 15% of chest radiographs of children with RSV pneumoni a compared with 76% of those in children with sole pneumococcal pneumonia ( P < 0.001). Patients with bacteremic pneumonia more often appeared ill (79% vs. 50%, P < 0.001) and more often had typical pneumococcal pneumonia with high fever, leukocytosis and lobar infiltrates in their chest radiographs (70% vs. 34%, P < 0.05) than those with serologically diagnosed pneumococca l pneumonia. Conclusions. Serologically detected pneumococcal pneumonia differs signific antly from RSV pneumonia in laboratory and chest radiography findings, but the clinical signs and symptoms overlap considerably. Bacteremic pneumococc al pneumonia is a more severe illness than the serologically diagnosed one.