Table 2. Recommended outcome and process indicators for a care cascade for active TB.
| Cascade stage | Outcome indicators for cascade steps (useful for monitoring program outcomes) | Methods or required data for outcome indicators | Process indicators for cascade gapsa (useful for understanding quality of care) | Methods or required data for process indicators |
|---|---|---|---|---|
| Stage 1: Reaching health facilities and accessing a TB test | Step 1: Number of individuals with incident or prevalent TB in the population | Gap 1: Number of individuals with TB who did not reach health facilities and access a TB diagnostic testb | ||
| Number of individuals with prevalent active TB in a population for each form of TB | Population-based TB prevalence survey, including drug-susceptibility testing and prior TB treatment history for diagnosed patients | Distance to nearest TB health facility as a surrogate measure of the proportion of individuals without access to TB servicesc | Questions asked to TB patients diagnosed in population-based prevalence surveys | |
| Annual number of individuals with incident active TB in a population for each form of TB | Modeling methods may facilitate estimation of incidence from active TB prevalence, surveys of the annual risk of TB infection, government case notifications, TB drug sales, or other data | Proportion who have not sought medical care | Questions asked to TB patients diagnosed in population-based prevalence surveys | |
| Time delays in care seekingd | In-depth interviews with individuals starting TB treatment at health facilitiesd | |||
| Number of individuals who died of TB without having received TB care | Population-based verbal autopsy surveys, including in-depth interviews with families of individuals who died of probable TB | |||
| Stage 2: Diagnosis | Step 2: Number of individuals with TB who reached health facilities and accessed a TB diagnostic testb | Gap 2: Number of individuals with TB who accessed a TB diagnostic testb but did not get successfully diagnosed | ||
| Number of individuals with smear-positive TB who accessed TB tests | Extrapolation from the proportion of patients who did not submit a second sputum sample (S1 Appendix) | Proportion of individuals with suspected TB who did not undergo any sputum testing | Audit of patient records at TB diagnostic facilities | |
| Number of individuals with Xpert-positive TB who accessed TB tests | Number evaluated equals the number diagnosed | |||
| Number of individuals with smear- or Xpert-negative TB who accessed TB tests or who had initiation of appropriate workup | Estimation based on the sensitivity of sputum microscopy or Xpert MTB/RIF in a given setting (S1 Appendix) | Proportion of individuals with suspected TB with negative sputum microscopy or Xpert test results who do not receive a medical diagnosis | Audit of patient records at TB diagnostic facilities | |
| Number of individuals with extrapulmonary TB who had initiation of appropriate workup | Estimation based on the anticipated rate of underdiagnosis of extrapulmonary TB in a given setting (S1 Appendix) | |||
| Number of individuals with MDR or RR TB who accessed TB tests | Extrapolation from culture-based studies estimating the proportion of MDR/RR TB among new and previously treated patients in a given setting (S1 Appendix) | |||
| Health system–related delays in diagnosisd | In-depth interviews with patients starting TB treatmentd | |||
| Stage 3: Linkage to treatment | Step 3: Number of individuals diagnosed with TBe | Gap 3: Number of individuals diagnosed with TB who did not get registered in treatment | ||
| Number of individuals with smear- or Xpert-positive (i.e., bacteriologically diagnosed) TB who were successfully diagnosed | Data on bacteriologically diagnosed pulmonary TB patients is usually efficiently captured in patient registers at diagnostic facilities | Proportion of patients lost prior to referral from a TB diagnostic facility to a treatment facility | Audit of diagnostic and referral registers at TB diagnostic facilities | |
| Number of individuals with smear-negative, Xpert-negative, or extrapulmonary TB who were successfully diagnosed | These patients have more prolonged diagnostic workups and may be listed in separate registers from bacteriologically diagnosed pulmonary TB patients, such as registers used to refer patients to treatment sites | Proportion of patients lost after referral from the TB diagnostic facility to a treatment facility | Audit of referral registers at TB diagnostic facilities and registers at treatment facilities | |
| Number of individuals with MDR TB or RR TB who were successfully diagnosed as having drug-resistant TB | These patients can be identified through lab registers recording drug-susceptibility test results. Otherwise, they may be misclassified as drug-susceptible TB patients | Delays in treatment initiationd | In-depth interviews with patients starting TB treatmentd | |
| Stage 4: Retention in treatment | Step 4: Number of individuals registered in TB treatmente | Gap 4: Number of individuals who did not complete TB treatment (due to treatment failure, loss to follow-up, or death) | ||
| Number of individuals registered (or notified) in TB treatment | TB treatment records or electronic registers | Proportion of patients who experience treatment failure, die, or are lost to follow-up in the intensive phase of therapy | TB treatment records | |
| Proportion of patients who experience treatment failure, die, or are lost to follow-up in the continuation phase of therapy | TB treatment records | |||
| Proportion of expected doses of TB medication actually taken during the treatment course (measure of the quality of medication adherence) [54] | TB treatment records | |||
| Stage 5: Post-treatment survival | Step 5: Number of individuals who completed TB treatmente | Gap 5: Number of individuals who experienced post-treatment TB recurrence or death | ||
| Number of patients who complete TB therapy | TB treatment records or electronic registers | Proportion of patients who experience TB recurrence or death within 1 year of treatment completion | Cohort studies involving close follow-up of patients every few months after treatment, with careful workup of new pulmonary symptoms, ideally with mycobacterial culture | |
| Proportion of patients with post-TB lung disease, including obstructive disease, restrictive/fibrotic disease, and pulmonary hypertension | Routine post-treatment follow-up of patients with spirometry and other measures of pulmonary function | |||
| Stage 6: Achieving durable cure | Step 6: Number of individuals who achieve 1-year recurrence-free survivale | |||
| Number of patients who survive for 1 year after completing TB treatment without disease recurrence | Cohort studies involving close follow-up of patients every few months after treatment up to 12 months, with careful workup of any new pulmonary symptoms, ideally with mycobacterial culture | |||
a Gaps can be estimated as the difference between two steps (i.e., Gap 1 = Step 1 − Step 2). The process indicators described in the table will further inform reasons for each gap.
b “Accessed a TB diagnostic test” refers to individuals with TB who either accessed an appropriate bacteriological test for TB or who had initiation of appropriate workup (for extrapulmonary or pulmonary TB patients who might be diagnosed empirically).
c Distance of a patient’s home from the nearest health facility is only one aspect of access to care; other factors include economic and social barriers, though these may be harder to measure routinely.
d Single in-depth interviews with TB patients at the time of treatment initiation can be used to capture information on delays in care seeking, diagnosis, and treatment initiation.
e Steps 3, 4, 5, and 6 are best estimated by following a single patient cohort, starting with diagnosed TB patients identified in Step 3 (i.e., a cohort-based or denominator–denominator linked approach).
Abbreviations: MDR, multidrug-resistant; RR, rifampin-resistant; TB, tuberculosis.