Bed-side infection screening of ICU patients using gram stained smears

Bronchial, abdominal or pleural aspirates (n = 364) collected from 165 ICU patients were both cultivated and evaluated microscopically using Gram stained smears, and the results were compared: 331 aspirates (91%) were classified correctly. Fungi were confirmed in all cases (21/21, sensitivity and specificity 100%). Gram-negative findings (n = 66) had a specificity of 97% (2/66 reclassified as Gram positive by culture): 21/85 Gram-negative cultures were overlooked by the Gram method (sensitivity 75%). Of 106 Gram-positive results, culture was negative in 10/106 and 7/106 were diagnosed as Gram-negative (specificity 84%). Sensitivity was 98% (only 2/91 not detected by the Gram technique). In 171 cases, no organisms were seen; specificity was 92% (Gram-negative bacteria cultivated in 14/171). Sensitivity was 94% (10/167 misdiagnosed as Gram-positive). Gram diagnoses were available 63 +/- 14 h prior to the culture test results. Treatment decisions based upon the Gram results were correct in 90% (326/364). It is concluded that Gram stained smears are a valuable tool for bed-side infection screening in ICU patients.