Quantitative gram stain interpretation criteria used by microbiology laboratories in Alberta, Canada.

Microbiology laboratories in Alberta, Canada, were surveyed to determine the quantitative interpretive criteria used to routinely read and report Gram stains. There was a wide variability in the quantitative reporting criteria cited for both cells and bacteria, with only 11 of 32 (34.4%) laboratories surveyed using the criteria recommended by the external proficiency-testing program. Lack of standardized criteria not only poses a problem in the grading of proficiency testing results but may also impact the quality of patient care.