House calls by community health workers and public health nurses to improve adherence to isoniazid monotherapy for latent tuberculosis infection: a retrospective study

Patient adherence to isoniazid (INH) monotherapy for latent tuberculosis infection (LTBI) has been suboptimal despite its proven efficacy. Various strategies have been studied to improve adherence, but all have been based at a clinic or treatment program. At the Santa Clara Valley Tuberculosis Clinic, it was our practice to refer a subset of high-risk LTBI patients to the Public Health Department for monthly follow-up at home instead of at the clinic. Our goal was to assess whether house calls by community health workers and public health nurses affected INH adherence or frequency of adverse effects.

We retrospectively studied 3918 LTBI patients who received INH. At the discretion of the treating physician, 986 (25.2%) received house calls instead of clinic follow-up. Home-based follow-up included language translation, medication delivery, assessment of compliance with pill counts, monitoring for adverse effects, and active tracking of noncompliant patients. We assessed differences in patient characteristics, treatment completion, and reasons for treatment discontinuation between patients followed at home versus in the clinic. Multivariate analyses to address possible referral bias or confounding were performed using logistic regression.

More patients followed with house calls completed INH treatment (90% home versus 73.2% clinic). This was the case across all subgroups of patients, including those with historically the lowest adherence: patients from correctional and rehabilitation facilities (77.8% home versus 46.9% clinic), postpartum women (86.4% home versus 55.6% clinic), and patients aged between 18 and 35 years (87% home versus 63.1% clinic). After adjusting for age, place of birth, referral category (TB contacts/skin test converters, correctional/rehabilitation patients, postpartum women, tuberculin positive patients from other screening), and prescribed INH regimen duration (9 versus 6 months), home-based follow-up of LTBI patients was a significant predictor of treatment completion (AOR 2.94, 95% CI: 2.33, 3.71). Patients followed at home were 21% more likely to complete therapy (ARR 1.21, p<0.001). Risk of adverse effects was similar between the two types of follow-up.

Home-based follow-up of LTBI patients taking isoniazid was associated with improved treatment completion and no increase in adverse effects regardless of patient characteristics or prescribed duration of INH therapy.