Forty-one TARs were published in the period studied, all of which contained a systematic review. Most of the economic evaluations (85 percent) were cost-utility analyses, reflecting NICE's guidelines for economic evaluation. In seventeen cases, the clinical data were not pooled in the review, owing to heterogeneity in the clinical data or the limited number of studies. In these cases, the economists used alternative approaches for estimating the key effectiveness parameter in the model