natural history

(Related concept: additive model) A model in which the combined effect of two or more factors is the product of the isolated effects of each factor. Note: For example, if a factor X multiplies a risk by a in the absence of Y, and if a second factor Y multiplies the risk by b in the absence of X, the combined effect of the two factors will be a x b.

and • provides information on costs and financial impact. Note 2: The report may optionally discuss organisational considerations. Note 3: A “mini-HTA” may be as rigorous as an HTA report but typically has a restricted scope and so is quicker to produce. Note 4: Related terms include health technology, HTA report, rapid review, level of evidence