Overview of current case
and treatment outcome definitions
Malgosia Grzemska
TB Operations and Coordination
Stop TB Department
Consultation
Impact of WHO-endorsed molecular diagnostics on TB and MDR-TB case- and
treatment outcomes definitions
Geneva, 12-13 May 2011
Outline
History of case and treatment outcome definitions
Current case definitions and treatment outcome
definitions
Commentary on current definitions
Next steps
History of case
and treatment outcome definitions
First introduced by Karel Styblo in Africa in pilot projects
of short-course chemotherapy
Confirmed by WHO in 1994 in the "Framework for
effective tuberculosis control" and recommended for use
in DOTS programmes worldwide
1998 – Europe started revision to facilitate use of culture
in diagnosis and monitoring
Each edition of WHO Treatment guidelines – slight
revision of definitions to "accommodate" new
developments in TB control
Current case definitions (WHO)
Definite TB case
– A patient with M. tuberculosis complex identified from a clinical
specimen, either by culture or by a newer method such as
molecular line probe assay.
– Pulmonary case with 1 or more initial sputum smear
examinations positive for acid-fast bacilli (AFB) - in countries
lacking lab. capacity to routinely identify M. tuberculosis
complex and with functional EQA system.
TB case
– A definite case of TB (as above); but also
– Patient in whom health worker (clinician or other practitioner)
has diagnosed TB and decided to treat the patient with the
whole course of anti-TB treatment
Treatment of tuberculosis: guidelines -- 4th edition, Geneva, WHO, 2009
Current case definitions (WHO) - 2
Classification according to
– Anatomical site of disease (P and EP)
– Bacteriological results (including drug resistance)
• Culture positive or Culture negative (both P and EP)
• Smear positive, smear negative, smear not done (only P)
– History of previous treatment
• New
• Previously treated: relapse, failure, default
• Transfer in
• Other
– HIV status
Commentary on case definitions
Definite case
– Smear microscopy not considered confirmatory test (though used
in resource poor settings)
– HIV positive patients – often smear negative
– Culture and newer tests added to "accommodate" availability of
tools other than smear microscopy
Previously treated
– Difference between relapses (new episode - incident) and other
retreatment's (same episode requiring change of regimen -
prevalent)
– Relapse true relapse or re-infection
Commentary on case definitions (2)
No one knows what to do with "transfer –in" – not
evaluated
Other – no standard interpretation
No information on groups with high risk of TB – which
may be required for decision making on appropriate
diagnostic and prevention intervention
Disaggregation according to social or other
determinants does not exist
No information on co-morbidities (other than HIV)
Current treatment outcome definitions (WHO)
Cure.
– A patient whose sputum smear (or culture) was positive at the
beginning of the treatment but who was smear- (or culture-)
negative in the last month of treatment and on at least one
previous occasion.
Completed.
– A patient who completed treatment but who does not have a
negative sputum smear (or culture) result in the last month of
treatment and on at least one previous occasion.
Treatment success
– is the sum of cure and completed.
Treatment of tuberculosis: guidelines -- 4th edition, Geneva, WHO, 2009
Current treatment outcome definitions (WHO)
Failure.
– A patient whose sputum smear (or culture) is positive at 5 months or
later during treatment.
– Also included in this definition are patients found to harbour a
multidrug-resistant (MDR) strain at any point of time during the
treatment, whether they are smear-negative or -positive
Default.
– A patient whose treatment was interrupted for 2 consecutive months
or more.
Died.
– A patient who dies for any reason during the course of treatment
Transfer out.
– A patient who has been transferred to another recording and
reporting unit and whose treatment outcome is unknown.
Commentary on treatment outcome definitions
Originally only smear positive cases were evaluated
Addition of "culture"; recommendations to evaluate smear-negative
and EP cases
Cure – only for smear positive (and culture positive); Failure – only
for smear positive (+ culture) and too late into the treatment course
If Xpert is the initial diagnostic test – less cases would be classified
cured (treatment monitoring with smear and/or culture)
Transfer – out – excuse for not following up (often default,
sometimes death, - but perceived a "better" outcome
Individual NTPs or regions (EU) revised case-or outcome
definitions
Non-evaluated – added for the purpose of global reporting
Conclusions – next steps
Transition from DOTS to Stop TB Strategy did not result in
changes in the definitions
Programmes add their own modifications, which may create
confusion and would hamper global reporting
Introduction of molecular tools in diagnosis of TB requires
modifications of case definitions and treatment outcome
definitions, else many cases may be not evaluated
Preparation for the introduction of new (shorter) treatment
regimens in the future