Table 4
Definitions of tuberculosis cases and treatment outcomes
A. Definitions of tuberculosis cases
Case of tuberculosis A patient in whom tuberculosis has been confirmed by bacteriology or diagnosed by a clinician.
Definite case A patient with positive culture for the Mycobacterium tuberculosis complex. In countries where culture is not routinely available, a patient with 2 sputum smears positive for acid-fast bacilli (AFB+) is also considered a definite case.
Pulmonary case A patient with TB disease involving the lung parenchyma.
Smear-positive pulmonary case A patient with at least 2 initial sputum smear examinations (direct smear microscopy) AFB+; or one sputum examination AFB+ and radiographic abnormalities consistent with active pulmonary tuberculosis as determined by a clinician; or one sputum specimen AFB+ and culture positive for M. tuberculosis.
Smear-negative pulmonary case A patient with pulmonary tuberculosis not meeting the above criteria for smear-positive disease. Diagnostic criteria should include: at least 3 sputum smear examinations negative for AFB; and radiographic abnormalities consistent with active pulmonary TB; and no response to a course of broad-spectrum antibiotics; and decision by a clinician to treat with a full course of anti-TB therapy; or positive culture but negative AFB sputum examinations.
Extrapulmonary case A patient with tuberculosis of organs other than the lungs (e.g. pleura, lymph nodes, abdomen, genitourinary tract, skin, joints and bones, meninges). Diagnosis should be based on one culture-positive specimen, or histological or strong clinical evidence consistent with active pulmonary disease, followed by a decision by a clinician to treat with a full course of anti-TB chemotherapy. Note: a patient in whom both pulmonary and extrapulmonary tuberculosis has been diagnosed should be classified as a pulmonary case.
New case A patient who has never had treatment for tuberculosis or who has taken anti-TB drugs for less than 1 month.a
Relapse case A patient previously declared cured but with a new episode of bacteriologically positive (sputum smear or culture) tuberculosis.
Re-treatment case A patient previously treated for tuberculosis, undergoing treatment for a new episode of bacteriologically-positive tuberculosis.
B. Definitions of treatment outcomes
(expressed as a percentage of the number registered in the cohort)
Cured An initially smear-positive patient who was smear-negative in the last month of treatment and on at least one previous occasion.
Completed treatment A patient who completed treatment but did not meet the criteria for cure or failure.
Died A patient who died from any cause during treatment.
Failed A smear-positive patient who remained smear-positive at month 5 or later during treatment.
Defaulted A patient whose treatment was interrupted for 2 consecutive months or more.
Transferred out A patient who transferred to another reporting unit and whose treatment outcome is not known.
Successfully treated A patient who was cured and and who completed treatment.
Cohort A group of patients in whom TB has been diagnosed, and who were registered for treatment during a specified time period (e.g. the cohort of new smear-positive cases registered in the calendar year 2003). This group forms the denominator for calculating treatment outcomes. The sum of the above treatment outcomes, plus any cases for which no outcome is recorded (e.g. still on treatment) should equal the number of cases registered. Some countries monitor outcomes among cohorts defined by smear and/or culture, and define cure and failure according to the best laboratory evidence available for each patient.
Footnote
a Cases reported as "history unknown" in the European Region are included as new cases in this report.