Table 9 Program priorities. Program priorities determined by decision analysis of the base case scenario, based on considering (1) improvement of evaluation rates by letters, phone calls, and home visits, (2) offering LTBI therapy to individuals in class TB2 or class TB4, (3) improving rates of starting LTBI therapy to those it is offered to (by education and outreach), and (4) improvement of rates of completion of LTBI therapy to those it is offered to (by targeted DOPT). Beginning with a minimal program (line 1), the available options (column two) were compared. Options that produced net health benefits and cost savings were always preferred over options that produced net health benefits at a net total cost; whenever more than one option produced health benefits and cost savings, we chose the option yielding the greatest savings (other choices of decision rule are possible). Options yielding health benefits at net cost were to be ranked according to the cost-effectiveness ratio. The resulting program actions are given in the left hand column of the following row, which forms the basis for the next comparison; notice that the costs and benefits of a given course of action (such as starting TB4s on LTBI therapy) depend on previous choices (such as whether or not we have sent letters to improve evaluation rates, yielding more TB4s to treat). The parameters and assumptions of the base case are discussed in the text and Appendix [Additional file 1].

Treat only active cases; detect them only passively

(1) Offer LTBI treatment to TB2s or TB4s, or

(2) send letters to improve evalua tion

Send letters (2.7 QALYs gained, $10 000 in net sav ings)

Send letters; treat active cases

(1) Offer LTBI treatment to TB2s,

(2) Offer LTBI treatment to TB4s, or

(3) make phone calls to improve evaluation rates

Treat TB4s (3.2 QALYs gained, $11 000 in net savings)

Treat active cases and TB4s; improve evaluation by letters

(1) Offer LTBI treatment to TB2s,

(2) make phone calls to improve evaluation rates further,

(3) improve rates of starting ther apy for TB4s, or

(4) improve completion rates by DOPT

Improve starting rates (1.3 QALYs saved, $1 800 in net savings)

Treat active cases and TB4s; improve evaluation rates by letters; improve starting rates

(1) send letters to improve evalua tion rates further,

(2) treat TB2s, or

(3) improve completion rates by DOPT

Treat TB2s (0.7 QALYs saved, $3 000 in net cost)

Treat active cases, TB2s, and TB4s; improve evaluation by letters; improve rates of starting therapy

(1) Further improve evaluation rates by phone calls, or

(2) improve rates of completing therapy (by targeted DOPT)

Phone calls (0.5 QALYs saved, approximately $1 000 in net savings)

Treat active cases, TB4s, and TB2s; improve evaluation by letters and phone calls

(1) Further improve evaluation rates by home visits, or

(2) improve rates of completing therapy by using targeted DOPT

Home visits (0.3 QALYs saved, approximately $1 000 in net cost)

Treat active cases, TB4s, and TB2s; improve evaluation by letters and phone calls

(1) improve rates of completing therapy by using targeted DOPT

> $100 000 per QALY saved; no further intervention