THE ECONOMICS OF DIAGNOSIS: THE COST-EFFECTIVENESS OF SCREENING TESTS FOR GESTATIONAL DIABETES MELLITUS

Purpose:

Gestational diabetes mellitus (GDM) is the most common medical complication of the pregnancy period. GDM is defined as carbohydrate intolerance of variable severity, with onset or first recognition during pregnancy. Screening for GDM is performed as early as possible in order to diagnose and treat pregnant women if necessary and to prevent short term complications and the future development of type 2 DM in the mothers and their offspring. This study was undertaken to determine the most cost-effective screening test strategy for GDM by comparing four alternative strategies with a strategy of “no screening”.

Method:

 A cost-effectiveness analysis was performed using a decision analytic model to estimate and compare costs and outcomes in terms of quality adjusted life years (QALYs) of screening tests for GDM. The outcomes were presented as one year QALYs for short-term complications and lifetime QALYs for type 2 diabetes mellitus. Combinations of screening and diagnostic tests in this study were explored and considered in terms of a negative dominant strategy (NDS) and a positive dominant strategy (PDS).

Result:

A universal screening strategy using 75g OGTT to confirm any positive RPG before treatment, recommended by SIGN 2001 and NDS, was found to have the greatest probability of being cost-effective for short term complications. The ICER for the SIGN 2001 strategy compared with the no screening strategy was £46, 760 per QALY gained. At the ceiling ratio of £30,000/QALY the probability that SIGN 2001 (NDS) is cost effective is 64%. PDS screening with risk factors followed by 75g OGTT, recommend by SING 2010, was cost-effective for long-term complications. PDS is cheapest and most effective strategy for long term complications at £4,110 and 80.95 QALYs.

Conclusion:

The NDS and PDS approaches allow the decision maker to consider the results of cost-effectiveness analyses in terms of the differences in FN (missed-diagnosis) and FP (over-diagnosis) test results. The trade-off between sensitivity and specificity or detection and unnecessary testing is at the heart of screening and diagnostic tests.