To examine the relative and absolute risk of primary hyperparathyroidism associated with incidental high ionized calcium levels in the general population, defined as levels above the normal range.
Key Findings:
2.5% of participants had moderately high or high plasma ionized calcium at baseline.
0.4% were diagnosed with primary hyperparathyroidism during follow-up.
Hazard ratios for primary hyperparathyroidism were 65 (95% CI: 46-92) for moderately high and 350 (95% CI: 251-489) for high plasma ionized calcium compared to low normal levels.
Absolute risks of primary hyperparathyroidism were 7.9% for women and 3.3% for men with moderately high calcium, and 44% for women and 21% for men with high calcium.
Interpretation:
High ionized calcium levels significantly increase the risk of primary hyperparathyroidism, indicating a need for further diagnostic evaluation in otherwise healthy individuals with incidental findings.
Limitations:
The study is observational and cannot establish causation.
Potential confounding factors may not have been fully accounted for.
The participation rate was only 43%, which may limit the generalizability of the findings to the broader population.
Conclusion:
The findings support the need for further diagnostic workup following incidental high plasma ionized calcium levels in the general population.
