Rapid Method Detects Urinary Tract Infections

The reliability of a rapid detection method for urinary tract infection (UTI) has been compared with the reference standard streaked agar plate method.

The novel CultureStat Rapid UTI Detection System (CSRUDS) consists of a vacuum-sealed glass ampoule containing trypticase soy broth dry media and triphenyl tetrazolium chloride, a chromophore indicator sensitive to dehydrogenase.

Scientists at Columbia University Medical Center, (New York, NY, USA) working with others, selected 980 clean catch urine samples into specimen cups during a 30-day period. Each specimen was streaked on separate 5% sheep blood agar plates and simultaneously a 7-mL aliquot of each fresh urine specimen was processed using the CSRUDS. A spectrophotometer linked to a computer and a bar code scanner was used to identify and test each urine sample.

Positive UTI conditions were accurately identified by both CSRUDS and agar streak plate methods. CSRUDS accurately identified UTI negative conditions with 99.3% reliability at 90 minutes. The negative predictive value of CSRUDS was 99.2% at 30 minutes. The bacterial plating results revealed that 413 (58.8%) of the CSRUDS negative group demonstrated no bacterial growth at all, and 289 (41.2%) of the CSRUDS negative group showed some degree of bacterial growth. Of the 289 samples, 82 (28.4%, including one of the six CSRUDS false-negative samples), showed bacterial growth in the 50,000 colony forming units (CFU) range and 200/289 (69.2%), including the other five false-negative CSRUDS samples, had CFU counts of 1,000-49,000 CFUs or mixed flora. Of the 289, 7 (2.4%) had growth greater than 100,000 colonies/mL.

The author concluded that he novel rapid detection system evaluated in this test program, the CSRUDS and MB80CSENC spectrophotometer (MicroBionetics, Eldersburg, MD, USA) provided UTI negative/positive same-day results within 90 minutes from the start of the test, with a highly reliable negative predictive value within 30 minutes for most patients. Because it is such a rapid test, contamination at urine collection is unlikely to affect the results of the assay. Specimen transport and delays in processing the urine sample are obviated because the test can be immediately performed in the urologist's office where the specimen was collected. The study was published in the April 2012 issue of the journal Urology.

Related Links:
Columbia University Medical Center
MicroBionetics