Rejection criteria for endotracheal aspirates from adults

Although criteria have been established to assess the quality of sputum specimens, no criteria for assessing the quality of endotracheal suction aspirates (ETSA) exist. Therefore, we compared the Gram stain (GS) and culture results for 504 consecutive ETSA specimens. Results recorded for GS included the numbers of squamous epithelial cells (SEC) and polymorphonuclear leukocytes (PML) per low-power field (LPF) (magnification, x100) as well as the quantities and types of organisms per high-power field (HPF) (magnification, x1,000). Culture results were quantitated by organism. Only 15% of ETSA specimens tested by GS contained > 10 SEC per LPF, and 21, 20, and 59% had < or = 10, 11 to 24, and > or = 25 PML per LPF, respectively. For 40% of ETSA specimens, no organisms were visible by GS. Of these specimens, 40% were sterile, 48% grew normal oropharyngeal flora (NF) only, 5% grew 1+ NF (i.e., > 10 colonies in the first quadrant) and 1+ gram-negative rods (GNR), and 7% grew < or = 1+ GNR either alone or in mixed culture. The mean numbers of organisms recovered from ETSA with < or = 10 SEC per LPF and > 10 SEC per LPF were 2.35 and 4.05, respectively. We therefore recommend that ETSA specimens that show no organisms by GS be rejected, in addition to those with > 10 SEC per LPF. Application of these rejection criteria enabled us to reject 847 (41%) of 2,068 ETSA specimens over a 6-month period. This represents a saving of approximately $66,000/year in unnecessary laboratory charges to patients.