Why MMR Was Once Used Extensively in Industrialized Countries?
MMR met the above criteria when TB was highly prevalent in industrialized countries.
Sensitivity: Excellent, in particular, with the use of mirror camera
Specifity: Depends on the skill of interpreters, which was generally good in these days
Reproducibility: Good with the production of standardized-ray machines
Feasibility: Easy to examine several hundreds within a few hours
Cost: Affordable to cover the cost in case of miniature films.
Acceptability: Good.
Safety: The detection rate was high, and its benefit was superior to the possible radiation hazard
Role and Limitation of MMR in TB Case-finding (1)
Role played by MMR in developed countries
MMR had been used as spear-head of TB control
In some countries, a mayor or head of town or village is asked to conduct MMR in a community under his jurisdiction, and it was useful to recognize his responsibility to carry out TB control. MMR in the community promted to organize voluntary associations for TB control.
Reasons why MMR was abondoned in low prevalence countries
Inefficiency: Detection rate came down, and MMR had become not cost-effective.
Quantitative limitation of MMR: Difficult to maintain high coverage of MMR
Qualitative limitation of MMR
Quality of miniature film
Quality of X-ray film reading
Quality and quantity of secondary examinations
Quality of guidance to detected patients
Role and Limitation of MMR in TB Case-finding (2)
Limitation of repeatedly carried out health examinations in defecting diseases
A model explaining role of repeatedly carried out health examinations in detecting diseases
Useful to detect slowly progressing diseases, and not useful to detect rapidly progressing diseases
Nature of TB
TB and symptoms: TB is not so asymptomatic as it was generally believed to be.
Rapid progression of TB: Approximately half of TB cases develops within 1 year
Spontaneous healing of TB: Many slight TB (abacillary and minimal extent) cure spontaneously
Going-up-stair like progression of TB
Why MMR Is Not Used Extensively in Developing Countries?
MMR in developing countries does not meet the criteria
Feasibility: Difficulties in the maintenance and repair of X-ray machines and the film supply
Cost: Developing countries can not afford the cost of MMR. Limited financial resources should be devoted for passive case-finding and treatment of detected cases
Priority in TB Case-finding
Social priority: Should cover whole country
Epidemiological priority: Smear (+) PTB as it is most dangerous source of TB infection and worst prognosis
Methods Used in TB Case-finding
Passive case-finding as a routine, and contacts examination, etc. as an additional method.
Industrialized countries: Screening by chest X-ray examination, and bacteriological examinations including cultrue to confirm diagnosis.
Developing countries: Screening by sputum smear examination, and referral of smear (-) respiratory symptomatics to higher level institutions
Tuberculin testing is useful to
