Case Study

D.C., a 27-year-old woman at 15 weeks' gestation, comes to your office for her first prenatal visit. She is accompanied by her 56-year-old mother, whom you treat for type 2 diabetes.

Case Study Questions

1. Which of the following is/are potential benefits of screening for and treating asymptomatic bacteriuria in D.C.?

   A. Lower incidence of symptomatic maternal urinary tract infections (UTIs).

   B. Lower incidence of bacterial resistance.

   C. Lower incidence of low–birth-weight infants.

   D. Lower incidence of preterm delivery.

2. Which screening method for asymptomatic bacteriuria is most appropriate?

   A. Urine dipstick analysis at this visit, followed by empiric treatment if leukocyte esterase or nitrite testing is positive.

   B. Urine dipstick analysis at all prenatal visits, with subsequent urine culture to guide antibiotic therapy if leukocyte esterase or nitrite testing is positive.

   C. Urine dipstick and culture at this visit, followed by empiric treatment while awaiting culture results.

   D. Urine culture at this visit, with subsequent antibiotic therapy if at least 10⁵ colony-forming units per mL of urine of a single uropathogen are found.

   E. Direct urine microscopy at this visit, followed by empiric treatment if gram-negative bacteria are identified.

3. Based on information from the U.S. Preventive Services Task Force (USPSTF), which one of the following statements about screening D.C.'s mother for asymptomatic bacteriuria is correct?

   A. She should be offered screening because she has type 2 diabetes, making her more likely to have asymptomatic bacteriuria.

   B. She should not be offered screening because treating asymptomatic bacteriuria in patients with diabetes does not improve clinical outcomes and is associated with potential harms.

   C. She should be offered screening because treating asymptomatic bacteriuria in patients with diabetes reduces the incidence of pyelonephritis and hospitalization for UTIs.

   D. She should be offered screening because the presence of asymptomatic bacteriuria in patients with diabetes has been shown to lead to hypertension and renal dysfunction.

   E. She should be offered screening because studies have not shown whether screening for asymptomatic bacteriuria in patients with diabetes is beneficial or harmful.

Answers

1. The correct answers are A and C. In pregnant women, detection of asymptomatic bacteriuria and treatment with antibiotics significantly reduces the incidence of symptomatic maternal UTIs and low birth weight. There is no evidence that screening for asymptomatic bacteriuria affects the incidence of bacterial resistance or preterm delivery.

The USPSTF recommends screening for asymptomatic bacteriuria with urine culture in pregnant women at 12 to 16 weeks' gestation or at the first prenatal visit, if later.

2. The correct answer is D. Urine culture is the standard criterion for detecting asymptomatic bacteriuria. There are currently no available tests with a high enough sensitivity and negative predictive value in pregnant women to replace urine culture as the preferred test. Dipstick analysis and direct microscopy have poor positive and negative predictive values for detecting bacteriuria in asymptomatic patients. The optimal frequency of subsequent testing is uncertain.

3. The correct answer is B. Although asymptomatic bacteriuria is more common in patients with diabetes, the USPSTF recommends against screening men and non-pregnant women. Good-quality studies have shown that treating these populations does not improve clinical outcomes. Treatment is also associated with potential harms, including adverse effects of antibiotic therapy and development of bacterial resistance. This recommendation applies to the general adult population, including adults with diabetes. Studies have not shown an association between the presence of asymptomatic bacteriuria and subsequent changes in creatinine clearance or the development of hypertension.