Economic evaluation of alternative testing regimes and settings to detect undiagnosed HIV in Australia

Table 1 Conventional Testing Regime: Private General Practice Clinic Setting – (Funded by Federal Government – Medicare)

	Probability of True HIV Positive (P_HIV)		Probability of True HIV Negative (1 *− P*_HIV)
Outcomes	HIV Positive (EIA+ & WB+)	False HIV Negative (EIA-)	False HIV Positive (EIA+ & WB-)	True HIV Negative (EIA-)
Probability of result	(P_HIV ∗ Sen_EIA ∗ Sen_WB)	P_HIV ∗ (1 − Sen_EIA)	((1 − P_HIV) ∗ (1 − Spec_EIA) ∗ Spec_WB)	(1 − P_HIV) ∗ Spec_EIA
Inputs
Visit 1: Initial Screening
Consult time	20 min	20 min	20 min	20 min
Medicate Rebate	$71.70¹	$71.70¹	$71.70¹	$71.70¹
Staffing	GP	GP	GP	GP
Pathology costs
EIA	$15.65²	$15.65²	$15.65²	$15.65²
WB confirmatory	$29.00³		$29.00³
Visit 2: Test Results
Consult time	40 min	20 min	20 min	20 min
Medicate Rebate	$105.55⁴	$71.70¹	$71.70¹	$71.70¹
Staffing	GP	GP	GP	GP
Total Cost of Each Outcome	$221.90	$159.05	$188.05	$159.05
Average cost (AC) per person tested	=(P_HIV ∗ Sen_EIA ∗ Sen_WB) ∗ AC per True HIV Positive_{EIA + , WB+} + (P_HIV ∗ (1 − Sen_EIA)) ∗ AC per False HIV Negative_EIA− + ((1 − P_HIV) ∗ Spec_EIA) ∗ AC per True HIV Negative_EIA− + ((1 − P_HIV) ∗ (1 − Spec_EIA) ∗ Spec_WB)) ∗ AC per False HIV Positive_{EIA + , WB−}
Average number of tests for a positive diagnosis	$ =\frac{1}{P_{HIV}\ast Se{n}_{EIA}\ast Se{n}_{WB}} $

Note: AC Average Cost, EIA fourth generation enzyme immunoassay test, GP General Practitioner, P Probability, Sen Sensitivity, Spec Specificity, WB Western Blot Test, + reactive test result, − nonreactive test result
1 = Medicare Rebate Item 36; 2 = Medicare Rebate Item 69,384; 3 = Medicare Rebate Item 69,387; 4 = Medicare Rebate Item 44

ISSN: 1472-6963