STONE Score Helps in Assessing Ureteral Stones

A five-item clinical prediction rule performs well in identifying patients with uncomplicated ureteral stones, according to a report in the British Medical Journal.

The score was developed in a retrospective cohort of 1040 adults undergoing noncontrast computed tomography (CT) for suspected uncomplicated kidney stones under a “flank pain protocol.” The factors associated with CT findings of symptomatic ureteral stones were incorporated into a scoring system identifying groups at low, moderate, and high probability of stones. The resulting 13-point STONE score was tested in a prospective validation cohort of 491 patients.

The five strongest predictors of ureteral stones were male sex, short duration of pain, nonblack race, nausea and vomiting, and microscopic hematuria. In the derivation cohort, the rates of ureteral stones were 8.3 percent in patients with a low-probability STONE score (0 to 5 points), 51.6 percent in those with a moderate probability score (6 to 9 points), and 89.6 percent in those with a high-probability score (10 to 13 points).

In the validation cohort, the rates were 9.2 percent, 51.3 percent, and 88.6 percent, respectively. Among patients with high-probability STONE scores, there was a 0.3 percent rate of acutely important alternative findings in the derivation cohort and 1.6 percent in the validation cohort.

Computed tomography is an accurate test for kidney stones, but it may not affect important clinical outcomes. The STONE score provides an easily calculated, objective clinical prediction rule for the assessment of renal colic patients.

The results suggest that the STONE score accurately predicts the likelihood of ureteral stones, which is inversely associated with the likelihood of acutely important alternative findings. With further validation, this score could help to select patients who could be treated without CT or with reduced-dose CT [More CL, et al. Derivation and validation of a clinical prediction rule for uncomplicated ureteral stone—the STONE score: retrospective and prospective observational cohort studies. BMJ 2014; g2191].

May 2014 (Vol. 6, Number 5)