Q-T INTERVAL AS PREDICTOR OF SERUM-CALCIUM LEVEL

To assess whether measurement of the electrocardiographic (ECG) Q-T in terval is a useful predictor of total serum calcium concentration, 15 uraemic patients were studied (10 female, five male; age range, 25-60 years). Resting ECGs were interpreted by three independent observers w ithout knowledge of the patients' identity or serum calcium. Three var iants of measurement of the Q-T interval were analysed, of which Q-(a) T(c), the interval from the beginning of the Q-wave to the apex of the T-wave, was the most consistent (coefficient of variation, 2.7%). Thi s also provided the best correlation with measured serum calcium conce ntration (P < 0.001). When compared to biochemical measurements, the p redicted serum calcium concentration was within 95% confidence limits in 14 of the 15 patients studied. However, the wide confidence limits of this technique mean that it cannot be recommended in routine clinic al practice.