Long-term follow-up of patients with elevated serum calcium concentrations in Swedish primary care.

Objective: To follow up patients with elevated calcium concentrations after 10 years.

Design: Longitudinal, using medical records, questionnaires, and clinical investigation.

Setting: Primary care in Tibro, Sweden, 2008-2010.

Subjects: 127 patents with elevated calcium concentrations and 254 patients with normal calcium concentrations from the local community, attending the health care centre.

Main Outcome Measures: Diagnoses and mortality in patients with elevated calcium concentrations in 1995-2000, compared with patients with normal calcium concentrations and the background population.

Results: The proportion of patients for whom no underlying cause was detected decreased from 55% at baseline to 12% at follow-up. Primary hyperparathyroidism was most common in women, 23% at baseline and 36% at follow-up, and the cancer prevalence increased from 5% to 12% in patients with elevated calcium concentration. Mortality tended to be higher in men with elevated calcium concentrations compared with men with normal calcium concentrations, and was significantly higher than in the background population (SMR 2.3, 95% CI 1.3-3.8). Cancer mortality was significantly increased in men (p = 0.039). Low calcium concentrations were also associated with higher mortality (p = 0.004), compared with patients with normal calcium concentrations.

Conclusion: This study underscores the importance of investigating patients with increased calcium concentrations suggesting that most of these patients--88% in our study--will turn out to have an underlying disease associated with hypercalcaemia during a 10-year follow-up period. Elevated calcium concentrations had a different disease pattern in men and women, with men showing increased cancer mortality in this study.