Tuberculosis Test Usage and Medical Expenditures from Outpatient Insurance Claims Data, 2013

Table 2

Summary regression results. Dependent variable: log of the medical expenditures of test for 86580 (TST) and 86480 (QFT-GIT). .

Independent variables	Coefficient [95% CI]	Transformed coefficient (%) [95% CI]
Age of patient	0.0048 [0.0045 to 0.0051]	0.48 [0.45 to 0.51]
Age-squared variable	−0.0000558 [−0.0000603 to −0.0000513]	−0.0056 [−0.0060 to −0.0051]
Quantity of services	0.16263 [0.1577 to 0.1676]	16.26 [15.77 to 16.76]
Gender
Male	Referent	Referent
Female	−0.0032 [−0.0059 to −0.0006]	−0.32 [−0.59 to −0.06]
Data supplier
Employer	Referent	Referent
Health plan	−0.0059 [−0.0091 to −0.0026]	−0.59 [−0.91 to −0.26]
Drug coverage?
No	Referent	Referent
Yes	−0.005 [−0.0086 to −0.0014]	−0.5 [−0.86 to −0.14]
Region
South	Referent	Referent
Northeast	0.1147 [0.1111 to 0.1183]	12.15 [11.75 to 12.56]
North Central	0.2134 [0.2092 to 0.2176]	23.79 [23.27 to 24.31]
West	0.2795 [0.2757 to 0.2833]	32.25 [31.75 to 32.75]
Unknown	0.1743 [0.1653 to 0.1833]	19.04 [17.97 to 20.12]
Health plan type
Comprehensive	Referent	Referent
Exclusive provider organization (EPO)	−0.0692 [−0.083 to −0.0553]	−6.69 [−7.96 to −5.38]
Health maintenance organization (HMO)	−0.007 [−0.0195 to 0.0056]	−0.7 [−1.93 to 0.56]
Point of service (POS)	−0.0478 [−0.0609 to −0.0348]	−4.67 [−5.91 to −3.42]
Preferred provider organization (PPO)	−0.0306 [−0.0428 to −0.0183]	−3.01 [−4.19 to −1.81]
POS with capitation	−0.1314 [−0.1502 to −0.1127]	−12.31 [−13.95 to −10.66]
Consumer driven health plan (CDHP)	−0.0795 [−0.0928 to −0.0662]	−7.64 [−8.86 to −6.41]
High deductible health plan (HDHP)	−0.0996 [−0.1129 to −0.0863]	−9.48 [−10.68 to −8.27]
Expenditures (difference)
86580 (TST)	Referent	Referent
86480 (QFT-GIT)	2.0627 [2.0587 to 2.0666]	686.72 [683.58 to 689.79]

Significance levels: ; . The -values associated with the coefficients were derived from bootstrap-generated standard errors with 50 replications. Because the dependent variables in the regression analyses were the natural log of dependent variable (medical expenditures), the coefficients were transformed as coefficient and interpreted as the relative change (in percentage) per unit change in the independent variable (IV) for the continuous IVs and as and interpreted as the relative difference (in percentage) in the estimated medical expenditures when compared with the referent (or omitted) category [13]. The brand names for the respective IGRA testing method CPT codes (i.e., QuantiFERON-TB Gold In-Tube [QFT-GIT] for 86480 and T-SPOT.TB [T-Spot] for 86481) were used because they were the only IGRA tests approved by the Food and Drug Administration (FDA) as of 2013 [7].