Blood tests not helpful for screening metabolic disorders in kidney stone disease, Study says

However, a full metabolic assessment with 24-h urine collection should be undertaken in recurrent stone formers and in those at high risk of future stone disease to identify potentially treatable metabolic abnormalities, explained Katie S Eyre and colleagues from the Department of Urology, Oxford University Hospitals NHS Foundation Trust, Oxford, UK.

The authors carried out this study with the objective to determine the clinical utility of blood tests as a screening tool for metabolic abnormalities in patients with kidney stone disease.

Clinical and biochemical data from 709 patients attending the Oxford University Hospitals NHS Foundation Trust for assessment and treatment of kidney stones were prospectively collected. Data were analyzed to determine the utility of serum calcium, parathyroid hormone (PTH), urate, chloride, bicarbonate, potassium and phosphate assays in screening for primary hyperparathyroidism, normocalcaemic hyperparathyroidism, hyperuricosuria, distal renal tubular acidosis (dRTA) and hypercalciuria.

The following results were noted-

2. An elevated serum calcium level was detected in 2.3% of patients.
3. Further investigations prompted by this finding resulted in a diagnosis of primary hyperparathyroidism in 0.2% of men and 4.6% of women for whom serum calcium was recorded.
4. An elevated serum PTH level in the absence of hypercalcaemia was detected in 15.1% of patients.
5. Of these patients, 74.6% were vitamin D-insufficient; no patients were diagnosed with normocalcaemic hyperparathyroidism.
6. Hyperuricosuria was present in 21.6% of patients and hypercalciuria in 47.1%.
7. Hyperuricaemia was not associated with hyperuricosuria, nor was hypophosphataemia associated with hypercalciuria.
8. No patient was highlighted as being at risk of dRTA using serum chloride and bicarbonate as screening tests.

Therefore, the authors concluded that "individuals presenting with renal calculi should undergo metabolic screening with a serum calcium measurement alone. Use of additional blood tests to screen for metabolic disorders is not cost-effective and may provide false reassurance that metabolic abnormalities are not present."