Patient Reported Outcomes Predicting Spontaneous Stone Passage May Not Have Acceptable Accuracy

We assessed the accuracy of patient reported outcomes for predicting spontaneous ureteral stone passage.

Patients with new unilateral ureteral calculi were prospectively assessed regarding current symptoms and whether they believed their stone had passed. The primary outcome was successful spontaneous stone passage as confirmed by ultrasound, and kidney, ureter and bladder x-ray. Spontaneous stone passage was compared to patient reported outcome responses to assess accuracy.

Of the 212 patients 105 (49.5%) had successful spontaneous stone passage at a mean followup of 17.6 days. Compared to the unsuccessful spontaneous stone passage group, those with successful spontaneous stone passage had significantly smaller (mean 5.4 vs 7.6 mm), more distal (71.4% vs 34.6%) stones with slightly longer average time to followup at first visit (19.2 vs 16.0 days). Additionally, there was more patient reported cessation of pain (77.1% vs 44.9%) and perceived stone passage (55.2% vs 13.1%) in this group. Cessation of pain was 79.7% (95% CI 67.1-89.0) sensitive and 55.8% (95% CI 44.0-67.1) specific for successful spontaneous stone passage. Likewise, patient reported stone passage was 59.3% (95% CI 45.7-71.9) sensitive and 87.0% (95% CI 77.4-93.5%) specific. In the multivariable logistic regression analysis cessation of pain (OR 4.02, 95% CI 1.91-8.47, p <0.01) and reported stone passage (OR 3.79, 95% CI 1.73-8.28, p <0.01) were independent predictors of successful spontaneous stone passage.

Cessation of pain and patient reported stone passage are independent predictors of successful spontaneous stone passage. However, both assessments may incorrectly gauge spontaneous stone passage, which raises concern for their validity as a sole clinical end point.