The analysis was based on a decision tree model with a one-month time horizon. The authors stated they adopted the perspective of a health management organisation.
Clinical inputs were taken from a previously published systematic review that included 706 patients: 346 in the vitamin D plus calcium group; 288 in the oral calcium group; and 72 in the control group (no treatment). The systematic review included only randomised clinical trials. Odds ratios were calculated for the comparison between the two prophylactic groups as compared to no treatment. The primary endpoint was presence or absence of symptomatic postoperative hypocalcaemia.
Monetary benefit and utility valuations:
Measure of benefit:
The summary benefit measure was defined as the proportion of patients without symptomatic postoperative hypocalcaemia.
The economic analysis included costs of medications (calcitriol, calcium carbonate, calcium gluconate) and medical services (emergency department visits, serum calcium measurement, hospitalisation). Costs born during both the acute and chronic phases were considered. Data on quantities of resources used were taken from a cohort of 13 patients who had presented postoperative hypocalcaemia at a first-level institution. Additional data were taken from published sources. Unit costs were obtained from the Colombian Social Security Institute’s billing manual for integrated care and the Colombian Manual of Pharmaceutical Products. Costs were in US dollars ($). The price year was 2008.
Analysis of uncertainty:
One-way sensitivity analyses were carried out on the probability of postoperative hypocalcaemia and treatment costs. A probabilistic sensitivity analysis was performed using a Monte Carlo simulation with 10,000 iterations and including random distributions for probabilities of hypocalcaemia, length of stay and costs. Cost-effectiveness acceptability curves were constructed.