Effectiveness score was given by the number of cases of tuberculosis prevented. The authors derived a method of valuation of health states which was based on patient compliance. This was determined as:
Good - no break in treatment, no visits more than 1 week late and positive results on more than 75% of urine tests;
Fair - no break in treatment, clinic visits can be 2 weeks late and positive results on 50-74% urine tests;
Poor - break in treatment, delay in visits and fewer than 50% positive urine tests.
A therapy effectiveness score equivalent to the degree of risk reduction for tuberculosis was calculated for each patient who was prescribed therapy. This score was determined as:
0 - duration of less than 6 months or 6-9 months with a compliance rate of fair or good;
0.4 - duration for 10-12 months with compliance rated fair or poor;
0.75 - duration for 6-9 months and compliance rated good;
and 0.93 - duration for 10-12 months and compliance rated good.