[Clinical microbiological study of sputum and aspirates from larynx or trachea. An evaluation of exact criteria for assessment by direct microscopy].

A prospective study of specimens of lower airway secretions was carried out in order to investigate the association of specimen quality and results of microbiological culture. The quality of expectorates (EXP) or aspirates from larynx/trachea (ALT) was assessed on the basis of numbers per low power field (< 1, 1-10, 11-25, and > 25) of squamous epithelial cells (SEC) and leukocytes, respectively. Specimens were classified as either acceptable, A (< or = 10 SEC), partly acceptable, B (11-25 SEC, > 25 leukocytes), or not acceptable, C (the remaining specimens). Six hundred and six specimens (385 EXP, 221 ALT) from 408 patients were included, and the distribution among categories was A 373 (62%), B 88 (15%), and C 144 (24%). For isolates of Streptococcus pneumoniae (n = 42) and Haemophilus influenzae (n = 51) there was a statistically significant association with specimen quality, and for aerobic bacteria including Pseudomonas aeruginosa a trend was noted. However, isolates of Enterobacteriaceae (n = 105), Staphylococcus aureus (n = 61), yeasts (n = 45) and Branhamella catarrhalis (n = 7) were not associated with specimen quality. It is concluded that a defined set of criteria allows a useful classification of EXP and ALT by direct microscopy and that it is justifiable not to cultivate specimens found not to be acceptable (category C).