Therapeutic Index (TIX) is a term that can be used in different ways. Schafter et al used it to compare intranasal corticosteroids used to treat allergic rhinitis. The authors are from multiple institutions in Germany.
Patient selection: allergic rhintis
therapeutic index for a steroid preparation =
= (measure of effectiveness) / (measure of safety and adverse effects)
The effectiveness was a summation score for 3 measures of efficacy, ranging from 0 to 9.
Measures of effectiveness:
(1) total nasal symptoms scores (0 to 3)
(2) total ocular symptoms scores (0 to 3)
(3) patient's global assessment (0 to 3)
The safety subscore was a summation score for 3 measures of adverse side effects, ranging from 0 to 9.
Measures of safety:
(1) epistaxis (0 to 3), probably also including local irritation
(2) long-term systemic effects on growth or serum cortisol levels (0 to 3)
(3) ocular side effects (0 to 3)
The higher the TIX the better the corticosteroid preparation.
While the index should work fairly well in most situations, special handling is needed for a score of 0 since division by zero can cause a division error.
