Is Simple Microscopy Useful in the Diagnosis of Asymptomatic Bacteriuria in Pregnancy in Primary Care Settings?

Abstract

Background: Booked antenatal care patients are often seen with routine urine microscopy result, but there are no locally defined guidelines for the primary care physician on how to use those results. The objective of the study was to establish whether the current practice of the diagnosis of ASB in pregnancy by urine microscopy among booked women at ECWA Evangel Hospital Jos was adequate, using urine culture as a gold standard.

Methods: A descriptive, cross sectional, facility-based study was carried out using a structured questionnaire administered to 184 patients between the ages of 17-42 years who gave informed consent. They had their socio-demographic data and relevant current and past medical history recorded. A physical examination was done measuring their temperature, eliciting for lower abdominal tenderness, renal angle tenderness and noting findings on speculum examination. Urine samples for urinalysis and urine culture were obtained using the clean catch mid urine technique. A white blood cell count per high power field of 2 or more seen under the microscope was considered significant for urinalysis and a single colony count of 10⁵ was considered significant for urine culture.

Results: The prevalence of ASB by urine culture was 4.9%. The correlation between urine culture and urine microscopy was 8.5%. A WBC/HPF of > 3 was found to be the most significant urine microscopy value that predicted a positive colony count. Using urine culture as a gold standard, microscopy > 2 WBC/HPF (current practice) gave a prevalence of 20.1%; sensitivity, 66.7%; specificity, 82.3%; PPV, 16.2%; NPV, 98.0%; and accuracy, 82.0%. Using > 3 WBC/HPF (proposed practice) however gave prevalence, 5.9%; sensitivity, 33.3%; specificity, 95.4%; PPV,27.3%; NPV, 96.5%; and accuracy, 92.4%.

Conclusion: In a setting where urine culture is not available, the use of microscopic urinalysis > 3WBC/HPF is an alternative in detecting ASB. However, in settings where urine culture is available, patients with > 2WBC/HPF should be requested to have a urine culture.

Keywords: Simple Microscopy, Useful, Diagnosis, Asymptomatic Bacteriuria, Pregnancy, Primary Care