Microscopic Analysis for Bacteriuria
The presence of bacteria in a fresh, Gram-stained specimen of uncentri- fuged urine correlates with 105 CFUs per mL in culture.37 An “enhanced uri- nalysis,” combining the counting chamber assessment of pyuria noted previously with Gram staining of drops of uncentrifuged urine, with a thresh- old of at least 1 Gram-negative rod in 10 oil immersion fields, has greater sen- sitivity, specificity, and positive predic- tive value than does the standard urinal- ysis33 and is the preferred method of urinalysis when appropriate equipment and personnel are available.
Automated Urinalysis
Automated methods to perform uri- nalysis are now being used in many hospitals and laboratories. Image- based systems use flow imaging analysis technology and software to classify particles in uncentrifuged urine specimens rapidly.38 Results correlate well with manual methods, especially for red blood cells, WBCs, and squamous epithelial cells. In the future, this may be the most common method by which urinalysis is per- formed in laboratories.