Evaluation of Growth Segregation Software for Automatic Interpretation of Urine Bi-Plate Cultures Comprised of Blood Agar and CHROMagar™ Orientation using WASPLab®

Full laboratory automation is a relatively new concept for microbiology laboratories.  One exciting aspect is use of digital imaging of culture plates combined with segregation software (SSW) to separate negative plates from positive plates.  We evaluated the COPAN WASPLab® and SSW with digital analysis of urine specimens inoculated to a bi-plate with blood agar and CHROMagarTM Orientation.  SSW was applied with image analysis at 0 hr and 20 hr incubation and was compared to manual Clinical Laboratory Scientist (CLS) read image analysis of the culture plates.

Discrepancies between SSW and CLS visual image analysis were resolved after review by a director.  A total of 5183 routine urine plates, processed by the WASPLab system according to standard laboratory procedures with a 1 µL loop were evaluated after 20 hr incubation at 35-37oC according to the following criteria: No growth (<1,000 CFU/mL=NG), <10,000 CFU/mL (<10IG, and considered negative for SSW), ≥10,000 CFU/mL (≥10 and considered positive), and multiple organisms present (MOP and if >10 considered positive).  There were 2032 urines considered negative (NG and <10IG) and 1680 considered positive by both CLS reading and SSW.  SSW called an additional 1471 positive while the CLS reading was considered negative (NG or <10IG) or insignificant (MOP).  Of these 1471 samples, 417 were visually read as <10IG, 55 were read as NG, and 999 were considered MOP by the CLS.

The plate images were further reviewed with >75% of the 417 50% of the 55 NG deemed accurate by the SSW.  Breakdown of the 2032 SSW negatives included CLS results of 1295 true NG, 726 <10IG, and 10 MOP (but <10IG).  There was only 1 culture out of 5183 called negative by SSW (false negative) that was considered positive by visual reading. Use of SSW to remove negative and insignificant growth urine cultures from the routine workflow should result in better laboratory efficiency and use of staff resources.  The Copan SSW is a powerful tool and can be applied with WASPLab® for bi-plate urine cultures with blood and CHROMagarTM Orientation agars.