Calcium
Sample Type: Any Body Fluid (e.g., serum, plasma, urine, cerebrospinal fluid, pleural fluid)
Overview:
Calcium is an essential mineral that plays a critical role in numerous physiological processes, including bone formation, muscle contraction, nerve impulse transmission, blood clotting, and cellular signaling. It exists in the body in two primary forms: bound (to proteins or anions) and free (ionized), the latter being the biologically active form.
Clinical Significance:
Calcium testing in body fluids is a vital diagnostic tool for evaluating metabolic and systemic disorders. While serum calcium is most commonly tested, calcium levels may also be measured in other fluids (e.g., urine, pleural fluid) depending on the clinical context.
Serum/Plasma Calcium: Assesses general calcium status and helps diagnose conditions like hypercalcemia and hypocalcemia. Total calcium includes both bound and free calcium; ionized calcium is measured separately for more accurate assessment of active calcium levels.
Urine Calcium: Used to evaluate kidney function, calcium stone risk, or metabolic calcium loss (e.g., in hyperparathyroidism).
Other Body Fluids (e.g., CSF, pleural fluid): Elevated or reduced calcium in these fluids may indicate local pathological processes such as infections, malignancies, or systemic calcium disturbances.
Common Conditions Associated with Abnormal Calcium Levels:
Hypercalcemia: Seen in hyperparathyroidism, malignancy, vitamin D toxicity, sarcoidosis.
Hypocalcemia: Occurs in hypoparathyroidism, chronic kidney disease, vitamin D deficiency, or after massive transfusion.
Testing Procedure:
Sample collection depends on the fluid being analyzed. For serum or plasma, blood is drawn from a vein. Urine samples are typically collected over 24 hours. For ionized calcium, special handling to avoid air exposure is needed.
Interpretation:
Normal Ranges: Depend on the fluid type and laboratory method.
Elevated Calcium: May suggest hyperparathyroidism, cancer, or granulomatous disease.
Low Calcium: May indicate renal failure, low vitamin D, or parathyroid hormone deficiency.
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