Serum calcium (S-Ca), the forgotten test: preliminary results of an appropriateness strategy to detect primary hyperparathyroidism (pHPT).

BACKGROUND

With the introduction of automated calcium measurements with multichannel continuous-flow analyzers in the 1970s, primary hyperparathyroidism (pHPT), the silent disease, began to be detected. Years later, with the first appearance of random access analyzers, laboratory tests were requested if the patient had clinical symptoms and pHPT was again overlooked. In this current scenario, serum calcium (s-Ca) is at risk of becoming a forgotten test. In consensus with endocrinologists and general practitioners (GPs), we implemented a strategy to detect asymptomatic pHPT patients.

METHODS

During a 9 month period, the Laboratory Information System automatically added s-Ca to every sample of blood from primary care patients older than 45 years, without a s-Ca request in the previous three years. If hypercalcemia was detected (albumin-corrected s-Ca > 2.6 mmol/L), phosphate, 25-hydroxy vitamin D and parathyroid hormone (PTH) were automatically processed in the same sample. We reviewed the medical record of every patient with hypercalcemia.

RESULTS

S-Ca was automatically added to 14,461 samples, with 79 hypercalcemia results. 14 hypercalcemia results with PTH levels in the reference range were clinically justified by causes other than pHPT. Of the remaining 65 patients, 41 were referred for evaluation by endocrinology. 34 resulted in a diagnosis of pHPT and 7 are currently in study. 24 patients were not followed by GPs to find out the primary cause of hypercalcemia. After a phone call from the laboratory, they are also currently being studied for hypercalcemia. Each case represented a cost of 110.4 US dollars.

CONCLUSION

Our proposed opportunistic screening to discover pHPT seems cost-effective.