Frequencies and patterns of microbiology test requests from primary care in Oxfordshire, UK, 2008-2018: a retrospective cohort study of electronic health records to inform point-of-care testing.

OBJECTIVES

To inform point-of-care test (POCT) development, we quantified the primary care demand for laboratory microbiology tests by describing their frequencies overall, frequencies of positives, most common organisms identified, temporal trends in testing and patterns of cotesting on the same and subsequent dates.

DESIGN

Retrospective cohort study.

SETTING

Primary care practices in Oxfordshire.

PARTICIPANTS

393 905 patients (65% female; 49% aged 18-49).

PRIMARY AND SECONDARY OUTCOME MEASURES

The frequencies of all microbiology tests requested between 2008 and 2018 were quantified. Patterns of cotesting were investigated with heat maps. All analyses were done overall, by sex and age categories.

RESULTS

1 596 752 microbiology tests were requested. Urine culture±microscopy was the most common of all tests (n=673 612, 42%), was mainly requested without other tests and was the most common test requested in follow-up within 7 and 14 days. Of all urine cultures, 180 047 (27%) were positive and 172 651 (26%) showed mixed growth, and was the most prevalent organism (132 277, 73% of positive urine cultures). Antenatal urine cultures and blood tests in pregnancy (hepatitis B, HIV and syphilis) formed a common test combination, consistent with their use in antenatal screening.

CONCLUSIONS

The greatest burden of microbiology testing in primary care is attributable to urine culture ± microscopy; genital and routine antenatal urine and blood testing are also significant contributors. Further research should focus on the feasibility and impact of POCTs for these specimen types.