Serum calcium measurement: Total versus free (ionized) calcium.

Measurement of serum free (ionized) calcium (Ca(++)) reflects true calcium status of the body in health and disease. Present study evaluates efficacy of Ca(++) over total calcium (CaT) in serum for calcium status. 52 subjects were enrolled for study. Anaerobic fasting blood sample for Ca(++) measurement and autoclaved plain bulb for estimation of CaT, Total protein (TP) and Albumin was used. CaT, Corrected CaT, Ca(++), Calculated Ca(++) were measured and correlated. Corrected CaT and calculated Ca(++) were derived from the measured parameters. Study group showed significant difference between CaT and corrected CaT (p<0.006), Ca(++) and calculated Ca(++) (p<0.001). Negligible correlation was observed between Ca(++) and serum protein. Positive correlation was observed between CaT and calculated Ca(++), TP and albumin. Findings indicate that Ca(++) levels are independent of serum protein status. With scrupulous sampling, Ca(++) may be a better parameter than presently used CaT for assessing calcium status in serum.