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Table 1 Key Parameters for Cost-Effectiveness Analysis

From: QuantiFERON-TB gold in-tube implementation for latent tuberculosis diagnosis in a public health clinic: a cost-effectiveness analysis

Variable Base-Case Low High Source
Epidemiologic/Diagnostic/Treatment Parameters     
Lifetime LTBI progression to active TB 5% 1% 15% [12, 13]
Percent of LTBI referrals that are foreign-born 64% 30% 100% [4]
Percent of QFT-GIT positivity in BCHD 57% FB; 36% US -- -- BCHD, [4]
Prevalence of LTBI in TST-positive referrals 70% FB; 43% US 0% 100% Calculated;[4]
Sensitivity of QFT-GIT 81% 36% 100% [8, 9, 14]
Specificity of QFT-GIT 99% 90% 100% [8]
Percent of LTBI patients treated with 4Rif 62% 0% 100% BCHD
LTBI treatment completion for 9INH (4Rif) 52% (73%) 25% 100% BCHD, [15, 16]
Drug-induced liver injury (percent severe) 1% (0.002%) 0% 6% BCHD, [13, 15, 1720]
Efficacy of LTBI treatment medications 0.9 0.50 1 [3, 17, 21, 22]
QFT-GIT Costs 2012 US$    
QFT-GIT tubes $7.10/test $6.60 $12.42 BCHD
Phlebotomy supplies and clinic supplies $2.18 $0.55 $3.82 BCHD
QFT-GIT kit $23.92/test* $9.90* $71.75* BCHD
QFT-GIT lab consumables $3.50/test $.87 $6.12 BCHD
Total equipment costs for QFT-GIT testing†† $1.14/test $.29 $1.99 BCHD
Phlebotomist labor for QFT-GIT $1.60/test $1.60 $3.99 BCHD
Laboratory labor for QFT-GIT $2.28/test $1.48 $2.52 BCHD
Overhead for QFT-GIT testing $0.53/sample $0.25 $2.50 BCHD
TB Treatment Costs     
Initial LTBI evaluation labor $35.04 $15.88 $68.29 BCHD
Labor LTBI treatment: 9INH $88.56 $36.40† $171† BCHD
Labor LTBI treatment: 4Rif $44.28 $18.20† $85.70† BCHD
Drug costs 9INH $26.82/course $9.27 $91.35 BCHD
Drug costs 4Rif $102.12/course $102.12 $482.60 BCHD
Chest x-ray $100 $50 $175 BCHD
Mild hepatitis $41.62 $0 $344 BCHD, [21]
Severe hepatitis $124.86 $41.62 $23,818 BCHD, [21]
Cost of active TB (includes drugs, staff, labs) $8,568 $2,142 $64,195 BCHD, [20, 21, 23]
Utilities     
Well 1    [21]
9INH treatment 0.95 .9 .99 [20, 21]
4Rif treatment 0.99 .9 .99 [20, 21]
Mild hepatitis 0.85 1 mo 12 mo [20, 21]
Severe hepatitis 0.40 0.1 0.4 [20, 21]
Active TB ** 0.85 0.5 0.9 [21]
Fatal TB ** 0.5 0.1 0.5 [21]
Death 0    [21]
  1. Note. LTBI = latent tuberculosis infection; TB = tuberculosis; QFT-GIT = QuantiFERON-TB Gold In-Tube; TST = tuberculin skin test; 4Rif = 4-month regimen of Rifampin; 9INH = 9-month regimen of Isoniazid; BCHD = Baltimore City Health Department records.
  2. * The base-case assumes a batch size of 24 patient samples per run. Low and high estimates are based on batch sizes ranging from 8 to 58 patient samples per run.
  3. † Low and high estimates based on variable staff salary and time spent per appointment.
  4. †† Includes costs for an Automated ELISA instrument, software, incubator, centrifuge, and other non-consumable laboratory equipment.
  5. **Sensitivity analyses incorporated range of utility weights, along with low and high estimates for life-expectancy after TB disease, and low and high estimates of TB related mortality.