Evaluation of two bioluminescence-measuring instruments, the Turner Design and Lumac systems, for the rapid screening of urine specimens

Abstract

Two bioluminescence-measuring instruments, the Turner Design and Lumac systems, were compared with a standard plate culture method for their ability to rapidly screen 400 urine specimens. For cultures with <1,000 CFU/ml the Turner Design, with old and new evaluation formulas, gave 6.5 and 50.6% false-positive results, respectively, versus 17.6% at-500 relative light units with the Lumac. For cultures which had >105 CFU/ml the Turner Design gave 39% (old formula) and 14% (new formula) false-negative results compared with 4% at <200 relative light units with the Lumac. The microorganisms most frequently isolated in the false-negative cultures from either system were gram-positive cocci. Predictive values for a positive test at > 105 CFU/ml were 77.4% (old formula) and 35.7% (new formula) for the Turner Design versus only 50% for the Lumac at .500 relative light units. Predictive values for a negative test for both instruments were >88 % at >105 CFU/ml. The Turner Design and Lumac systems were 4.0 and 3.7 times as expensive, respectively, as the plate culture method. Although both systems greatly reduce the time required to process urine specimens, their high costs as compared with that of plate culture, their failure to detect many specimens having > 105 CFU of gram-positive cocci per ml, and the numerous false-positives reported by both instruments suggest that additional improvements in the systems are warranted.

Bioluminescence screening for bacteriuria

“…Several recent evaluations of the Lumac system have been published (3,8,14,15). In these studies the critical parameters have ranged as follows: sensitivity, 88.9 to 96.4%; specificity, 75.0 to 88.7%; predictive value of negative results, 69.0 to 99.3%; predictive value of positive results, 50.0 to 96.0%.…”

“…This ATP can be detected by the bioluminescence produced in the firefly luciferin-luciferase reaction: Work with the bioluminescence ATP assay in the early and mid-1970s was discouraging due to lower sensitivities compared with the calibrated loop technique, interference from nonbacterial sources of ATP, and high cost (2). Recently, the 3M Co. has marketed the Lumac Biocounter M2010 Multi-Jet and the Lumac kit, containing reagents that selectively isolate and destroy the mammalian ATP before the actual assay of bacterial ATP. Several evaluations of this system have now been published (3,8,14,15). The types of hospitals and patient populations have varied among the different studies, as have the results.…”

Leukocyte esterase-nitrite and bioluminescence assays as urine screens

“…Bioluminescence used for the detection of significant bacteriuria is highly effective (4,26,28,29) and is superior to the LE-nitrite tests in sensitivity and specificity (7,18). In the present study, bioluminescence was more efficient in detecting significant bacteriuria than the LE-nitrite tests, and there were fewer false-positive and false-negative results (Table 1).…”

Detection of urinary tract infections by rapid methods.

“…Clinical evaluations of the systems reported sensitivities of >92% at 2105 CFU/ml and >85% at 2104 CFU/ml (2,19,26,52,54,61,62,74,86,88,89,96,97). The total cost per test for Lumac and the Monoscreen systems, which includes reagent cost, technical time, and cost of plating true and false-positives, was estimated at $2.50 or $1.77 for reagents or consumables alone, compared with $0.97 for the UTI screen.…”