Hypocalcemia and Vaso‐Occlusive Painful Crises in Pediatric Sickle Cell Anaemia

Abstract

Background: Low serum calcium (hypocalcemia) occurs in sickle cell anaemic (SCA) children. Concomitant presence of prolonged corrected QT (QTc) interval on electrocardiogram can ascertain hypocalcemia, especially during vaso-occlusive painful crises (VOC).

Aim: The aim of the study was to determine the relationship between hypocalcemia and VOC.

Methods: It was a prospective cohort study of 38 SCA children aged 4–17 years during VOC and when the same children were in steady state. Information regarding bone pain and clinical examination were obtained, following which electrocardiography was done during both clinical states. Blood was drawn for total calcium and serum albumin estimation.

Results: The mean (standard deviation [SD]) of total calcium was significantly lower during VOC (1.90 [0.19] mmol/l) than during follow-up steady state (2.24 [0.22] mmol/l), P < 0.001. The mean rank of QTc interval was significantly higher during VOC (19.93) than in follow-up steady state (14.50), P < 0.001. Total calcium negatively correlated with QTc intervals during VOC (r_s[36] = −0.36, P = 0.029) and follow-up steady state (r_s[36] = −0.49, P = 0.002), while QTc interval was highly predictive of hypocalcemia (area under the curve [AUC] = 0.82, P < 0.001). Similarly, total calcium was highly predictive of VOC (AUC = 0.89, P < 0.001) at cutoff point of 2.13 mmol/l with 89.5% sensitivity and 81.6% specificity. Hypocalcemia was significantly observed during VOC than follow‐up steady state (89.5% vs. 21.1%, P < 0.001) with odds ratio of 21.28 (95% confidence interval: 0.012–0.189; P < 0.001).

Conclusion: Total calcium <2.13 mmol/l is associated with VOC. Regular total calcium tests should be done. SCA children may benefit from routine oral calcium to reduce frequency of VOC.