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Increase in dialyzable calcium associated with therapy with lithium
Insights
Dialyzable calcium testing reveals higher hypercalcemia rates in lithium patients than total calcium alone suggests. This finding highlights potential underdiagnosis of mild hypercalcemia in individuals on oral lithium therapy.
Area of Science:
- Clinical Chemistry
- Endocrinology
- Pharmacology
Background:
- Lithium therapy is common for psychiatric disorders.
- Hypercalcemia can be associated with lithium use.
- Accurate assessment of calcium levels is crucial in these patients.
Purpose of the Study:
- To compare total and dialyzable calcium concentrations in patients undergoing routine lithium analysis.
- To determine the incidence of hypercalcemia in patients receiving lithium therapy using both calcium measurement methods.
- To assess the utility of dialyzable calcium in identifying mild hypercalcemia potentially missed by total calcium measurements.
Main Methods:
- Consecutive serum samples from patients for lithium analysis were tested for total and dialyzable calcium.
- Reference intervals for total calcium (2.20–2.58 mmol/L) and dialyzable calcium (1.30–1.47 mmol/L) were established.
- Calcium levels were also measured in a control group of apparently healthy volunteers.
Main Results:
- 33% of patient samples showed elevated dialyzable calcium, compared to only 6.1% with elevated total calcium.
- No healthy volunteers had calcium levels outside the reference intervals.
- Elevated calcium levels in patients were not attributable to age or sex differences.
Conclusions:
- Dialyzable calcium measurement is more sensitive in detecting mild hypercalcemia in patients on lithium therapy.
- A significant proportion of patients on oral lithium salts may have undiagnosed mild hypercalcemia.
- Routine assessment of dialyzable calcium could improve the detection and management of hypercalcemia in lithium-treated individuals.
Abstract:
We measured total and dialyzable calcium concentrations in consecutive sera submitted for routine lithium analysis. Of 98 samples from 61 different individuals, six (6.1%) total calcium results and 32 (33%) dialyzable calcium results were above the respective reference intervals. By comparison, when both total and dialyzable calcium were measured on 50 different apparently healthy volunteers, no results were outside either reference interval (2.20--2.58 mmol/L for total and 1.30--1.47 mmol/L for dialyzable calcium). These increases were not due to age or sex differences between the patients and controls. From the dialyzable calcium data, there appears to be an even higher incidence of mild hypercalcemia in patients receiving oral lithium salts than is indicated by the total calcium concentration alone.