Cost-Utility Analysis of Mycophenolate Mofetil versus Azathioprine Based Regimens for Maintenance Therapy of Proliferative Lupus Nephritis
Table 1
(a) Base-case three-year model inputs of probability parameters (Cochrane data). (b) Three-year model inputs of direct and indirect costs. (c) Three-year model inputs of utility parameters.
(a)
Probability parameters (over 6-month period or one cycle)
Mean
Range (95% CI)
Probability distribution
Sources
Remission AZA
Probability of lupus-related death during remission
AZA: azathioprine; MMF: mycophenolate mofetil; CYC: cyclophosphamide; ESRD: end stage renal disease; CI: confidence interval. Probabilities from the data sources were reported over various follow-up durations. Probabilities were converted to rates and then to 6-month probabilities [15]. First, the probabilities were converted to yearly rates (event per patient per year) using the equation , where = rate; = time in years; = probability of an event occurring during time . These annual rates were then converted to 6-month probabilities using the equation , where = one-year rate; = time in years; = probability of an event occurring during time . Beta distributions are characterized by (, ).
AZA: azathioprine; MMF: mycophenolate mofetil; CYC: cyclophosphamide (intravenous); ESRD: end stage renal disease; USRDS: United States Renal Data System; LN: lupus nephritis. Based on unit cost of AZA 50 mg tablet = $1.41 (range 0.63–4.81) [12]. Based on unit cost of MMF 500 mg tablet = $6.64 (range 1.56–7.93) [12]. Based on monthly cost of intravenous CYC 0.75 gm/m2 = $1038.92 [12, 16]. See Supplemental Table 6: costs of individual components of intravenous cyclophosphamide infusion. Components of direct costs included care provided by specialists, nonspecialists, nonphysician healthcare professionals, laboratory studies, imaging studies, emergency room visits, outpatient surgery, and hospitalizations [18]. Indirect costs included time lost from labor and nonlabor (i.e., household work) market activity as well as time that a caregiver spent helping the patient receiving healthcare services and the time the caregiver spent doing housework [19]. Gamma distributions are characterized by ; , , where = mean; = variance.
AZA: azathioprine; MMF: mycophenolate mofetil; CYC: cyclophosphamide (intravenous); ESRD: end stage renal disease; TTO: time trade-off; VAS: visual analog scale. Disutility = 1 − utility weight. Based on 95% confidence interval or standard deviation. Beta distributions are characterized by (, ).