Clinical evaluation of the Lumac bioluminescence method for screening urine specimens

Abstract

A bioluminescence method for screening urine cultures of provide rapid reporting of negative specimens and to select appropriate urine cultures for direct application of automated identification methods was evaluated. A total of 2000 specimens were processed in the Lumac Biocounter, and the results were compared with quantitative culture techniques by using a 0.001-ml inoculating loop. A total of 841 specimens were positive by the bioluminescence method; 291 specimens were culture positive (.gtoreq. 50,000 colony-forming units of 1 or 2 organisms/ml). Positive cultures represented > 20 different bacteria. Of the false-positive results .apprx. 2/3 represented mixed flora or pure cultures of < 5 .times. 104 organisms/ml. The predictive value of a negative result was 98.4%, reflecting a false-negative rate of only 0.7%. No advantages in cost or technician time were noted, but the Lumac method appears to be a useful technique in decreasing reporting time, especially for negative urine cultures.