Stone recurrence predictive score (SRPS) for patients with calcium oxalate stones

Purpose: We developed a convenient, self-administered 8-item stone recurrence predictive score (SRPS) to predict the recurrence of calcium oxalate stones. Materials and Methods: An 8-item SRPS to predict stone recurrence was developed based on general patient data, including age, sex, urine volume, smoking, wine drinking, family history, stone number and history of gouty arthritis. Mean age of the 204 studied patients with calcium oxalate stones +/- SD was 59.4 +/- 14.5 years (range 24 to 83). The male-to-female ratio was 3:1. Of the patients 115 were recurrent stone formers and 89 were single stone formers. We compared all available general data in the recurrence and control groups. Results: Family history, stone number, gouty arthritis and SRPS were independent risk factors for stone recurrence. Mean SRPS in recurrent and single stone formers was 7.6 +/- 3.1 and 5.1 +/- 2.0, respectively (p = 0). An increase in SRPS had a significant positive correlation with stone recurrence (r(2) = 0.859, p < 0.0001). At an SRPS cutoff of 7 or greater we achieved 61.7% sensitivity and 75.3% specificity to predict stone recurrence. At an SRPS of 11 or greater we found that 100% of patients had recurrent stones. Conclusions: With the introduction of the 8-item SRPS we provide a simple, convenient and reliable tool to predict calcium oxalate stone recurrence. Due to the characteristics of the high incidence of stone recurrence thorough metabolic evaluation may be justified in patients with an SRPS of 7 or greater and preventive measures are highly recommended in those with an SRPS of 11 or greater.