The Threshold Approach

The decision to test for or treat disease depends on the patient’s likelihood of having the disease and the clinician’s threshold for action, an idea known as the threshold approach to clinical decision making:  

Source: Pauker et al. The threshold approach to clinical decision making. N Engl J Med. 1980

To use UTIs as an example, a patient with a probability of UTI below the testing threshold should not undergo a urine culture.

A recent study applied this idea to clinical decision making by surveying a group of primary care clinicians (551 total, consisting of attending and resident physicians, NPs, and PAs) about a low-risk scenario for UTI: a 65-year-old man presents with foul-smelling urine, trace blood on dipstick, and no pain or dysuria. 

Clinicians were asked whether they would obtain a urine culture and treat if the culture were positive. They were also asked to provide a risk estimate for each outcome. (For this scenario, which describes asymptomatic bacteriuria, IDSA guidelines would not recommend a urine culture and would not recommend antibiotics even if the culture were positive.)

Source: Harris et al. Clinician Testing and Treatment Thresholds for Management of Urinary Tract Infection. Open Forum Infect Dis. 2023
  • 61% of respondents indicated that they would test with a urine culture. Yet based on clinician estimates of the probability of UTI, the probability at which ≥50% of clinicians would order a urine culture was a 19.1% chance of UTI
  • In the presence of a positive urine culture, 71% indicated that they would treat for UTI with antibiotics. Yet the overall treatment threshold following a positive urine culture was estimated to be a 42.3% chance of disease

Given the high estimates of probability of UTI, it appears that most clinicians perceived the scenario as UTI, allowing for the calculation of testing and treatment thresholds. The study asked clinicians to assign probabilities of disease while simultaneously deciding whether to treat. Respondents may have reported a probability that matched their decision to treat, rather than first assigning a probability of disease.

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