Sputum screening by Nomarski interference contrast microscopy.

Gram-stained smears of specimens submitted for sputum cultures were compared with direct wet mounts examined by Nomarski interference contrast microscopy (NIM) for enumeration of squamous epithelial cells (EPC) and leukocytes (WBC). The results obtained by the two methods were comparable, but specimens were more rapidly screened and cell types were more readily differentiated by NIM. Specimens submitted for sputum culture over a 3-month period were examined for EPC and WBC by NIM. Twenty-two percent of the specimens had greater than 25 EPC/field or a predominance of EPC (class I), 30% had greater than 25 EPC and greater than 25 WBC/field (class II), and 48% had greater than 25 WBC/field or a predominance of WBC (class III). The clinical relevance of the culture results was determined by reviewing the records of patients whose specimens were included in the study. Class I specimens provided only 30% clinically relevant culture results. Specimens in class II provided useful culture results in 63% of the patients, and 96% of those in class III provided clinically relevant information. The results confirm the value of sputum screening and demonstrate that NIM provides a rapid, simple, and accurate method for sputum screening.