Predictors of Compliance for Treatment of Latent Tuberculosis Infection and Cost Analysis at a County Health Department in Kentucky

Background: The CDC recommends that health departments (HD) perform targeted testing and treatment for Latent Tuberculosis Infection (LTBI) to decrease the occurrence of Tuberculosis (TB) disease. While public health state laws ensure treatment compliance of persons with TB disease, no such laws exist for ensuring compliance for LTBI treatment. Therefore, it is vital to determine likely indicators of treatment completion. Also, there has been very little published data on the cost of resource utilization by HDs in following this CDC mandate. 

Objective: The objectives of this study were to assess the factors associated with compliance for LTBI among high risk patients at a HD and to evaluate the treatment program cost.

Methods: Six hundred patients treated for LTBI between 2006 and 2009 were included in the study. Demographics, medications, laboratory tests, completion of treatment, and frequency of clinic appointment were obtained from medical records. A multivariate logistic regression analysis was performed to identify factors associated with completion of at least 6 months of Isoniazid (INH) or 4 months of Rifampin treatment. The total cost of the program was calculated by amassing costs related to chest X-rays, staff time, laboratory tests, medications, and use of interpreter services. A cost associated with noncompliance was also calculated by assessing all medical charges accrued by patients who failed to complete the prescribed course.    

Results: Out of the 600 study participants, 391 (65%) patients completed at least 6 months of INH or 4 months of Rifampin. Multiple logistic regressions showed that race, birth place status, and the client’s reason for obtaining the Tuberculin Skin Test (TST) were significantly related to completion of treatment. Asians (OR=1.92, 95%CI=1.07-3.47) and foreign born persons (OR=0.58, 95%CI=0.35-0.96) were more likely to be compliant in treatment of LTBI than their counterparts. Those who obtained the TST for immigration status were more compliant than those who obtained the TST for employment (OR=0.52, 95%CI= 0.27-0.98), contact of an active TB case (OR=0.39, 95CI%=0.20-0.78), incarceration (OR= 0.23, 95CI%= 0.07-0.79), and homelessness (OR= 0.24, 95%CI= 0.09-0.67). The cost of the program was about $116,687 and the cost associated with noncompliance was $24,266 (21% of total cost).

Conclusions: Although 65% completion rate is comparable to rates reported in the literature, HDs with limited resources can ill afford to expend 21% of the budget on persons who meet targeted testing criteria but remain noncompliant. Therefore, interventions should be aimed at persons who are less likely to be compliant. Persons who may be noncompliant include white patients and U.S. born patients. Patients who obtain the TST for employment, contacts of active TB cases, are incarcerated or homeless may also be at risk for noncompliance.