Transcript On-site Evaluation

Role of Laboratory Services
in TB Control
Dr Mohammad Rahbar
Professor of Microbiology
Department Microbiology
Reference health Laboratory ,Tehran iran
National Laboratory Infrastructure
Ministry of Health
National Reference Laboratory
Province Laboratories
District Laboratories
Health Centers
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Desirable Features of
Diagnosis Methods in TB
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Sensitivity
Specificity
Predictive value
Speed
Reliability
Reproducibility
Cost
Safety
Easy to use
Robustness
Widest usage
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What is new in the diagnosis of TB
TRC/ICMR
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AFB smear
AFB (shown in red) are tubercle bacilli
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Aims of sputum microscopy

Diagnosis of patients with infectious
tuberculosis
 Monitoring progress of patients on
treatment
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Advantages of sputum
microscopy
 More reliable than x-ray
for the diagnosis of infectious TB
 Simple to perform
 Easy to read
 Minimal infrastructure required
 Inexpensive
 Quick
 Only tool to monitor and declare
patients as “cured’’
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Diagnosis of pulmonary
tuberculosis
Three specimens optimal
Spot specimen on first visit;sputum
container given to patient
Early morning collection next day
Spot specimen during second visit
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Three sputum smears are optimal
Cumulative Positivity
100
93
100
Second
Third
81
50
0
First
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A good smear
 Made from mucopurulent sputum
 Spread evenly
 3 cm x 2 cm in size
 Not too thick
 Thin enough to read newsprint through
 Air dried before fixing
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False negative results
 Inadequate sputum collection
avoid – saliva, nasal discharge
collect – bronchial sputum from depth of chest
 Inadequate storage of sputum / stained smears
exposure to direct sunlight
radiation ( UV light )
excessive heat / humidity
 Not taking mucopurulent portion of sputum
 Inadequate smear preparation
 Inadequate smear examination
 Administrative & recording errors
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Consequences of false
negative smear results
 Patients with TB will not be treated, resulting in
suffering, spread of TB and death .
 Intensive phase of treatment will not be
extended for the required duration, resulting in
inadequate treatment
 Patient may lose confidence in the
programme
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False positive results
 Food particles
 Precipitated stains
 Saprophytic AFB
 Spores of B.subtlis
 Fibres and pollen
 Scratches on slide
 Contamination through carry over of
AFB from one smear to another
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Consequences of false positive
results
 Patients are started on treatment unnecessarily
 Treatment is continued longer than necessary, in
follow-up examinations
 Medications will be wasted
 Patients lose confidence in the programme
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QUALITY ASSURANCE PROGRAM
(QAP )IN SPUTUM SMEAR
MICROSCOPY
Quality Assessment
• Also called External Quality Assessment
(EQA)
• A process that allows participant
laboratories to assess their capabilities by
comparing their results with those in other
laboratories in the network .
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EQA
• Activities
– On-site evaluation of the laboratory,
– Panel testing and
– Blinded cross checking or Random Blinded
Cross Checking (RBCC)
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Feedback
• A process of communicating results of EQA
to the original laboratory, including
suggestions for possible causes of errors
and remedies.
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High False Results
• High False Negative (HFN).
– A 1+ to 3+ positive smear that is misread as
negative. This is a major error.
• High False Positive (HFP).
– A negative smear that is misread as 1+ to 3+
positive. This is a major error.
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Low False Results
This type of minor error occurs occasionally
even in laboratories that are performing
well.
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Low False Results
• Low False Negative (LFN).
– A scanty (1- 9 AFB / 100 fields) positive smear
that is misread as negative.
• Low False Positive (LFP).
– A negative smear that is misread as a scanty (19 AFB / 100 fields) positive.
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Quantification Error (QE)
• Errors seen in grading of positive slides.
• Difference of more than one grade in
reading a positive slide between examinee
and controller.
• This is considered as a minor error that
generally has no impact on case
management.
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EQA
Three methods to evaluate laboratory performance:
• On-site evaluation
• Panel testing
• Blinded rechecking
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EQA
Three methods to evaluate laboratory performance:
• On-site evaluation
• Panel testing
• Blinded rechecking
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On-site Evaluation
• Contents of a On-site evaluation checklist.
• General Information.
• Action required to be taken in the previous
visit.
• Current visit particulars.
• Panel testing of slides, if required.
• Assessment of EQA responsibilities of lower
level supervisor.
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On-site Evaluation..
• Availability of patient slides.
• Proper storage for EQA.
• Adequate training of staff with refresher
courses.
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Panel Testing
For assessment of proficiency in staining
and or reading.
Least expensive and resource intensive of
the 3 methods of EQA.
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Panel Testing
• Preparation from known patients’ specimen.
• Manufacture of slides with required grade
of smears.
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Manufacture of Panel Testing
Slides
• To be done at National ReF Lab.
• Collection of negative and high grade
positive patients specimen.
• Addition of Formalin to stabilize the pus
cells and to render the specimen safe for
handling.
• Liquefaction of specimen using NALC.
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Manufacture..
• Mixing of positive and negative specimens
to obtain the a known number of AFBs and
pus cells in the specimen.
• Preparation of slides.
• Validation of a sample of specimen for
consistency of the results.
– Results to match to an extent of at least 95%.
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Panel Testing..
Limitation:
Checks only technicians ability to stain and/
or read smears not a useful means to assess
routine laboratory performance
Not required as a routine if Blinded
Rechecking is done.
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Panel Testing..
• Panel testing is useful to:
– Supplement rechecking program.
– Provide some preliminary data on peripheral
laboratory capabilities prior to implementing a
rechecking program.
– Asses current status of performance or to quickly detect
problems associated with very poor performance.
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Panel Testing..
– Evaluate proficiency of laboratory
technicians following training.
– Monitor performance of individuals when
adequate resources are not available to
implement a rechecking program.
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Random Blinded Rechecking
• The most important method in EQA.
• Controller and reading from high level lab for
peripheral microscopy centers (MCs).
• A country wide program for blinded rechecking of
slides at regular intervals.
• A long term goal for optimal EQA.
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Lot Quality Assurance Sampling
• A blinded rechecking sampling method.
• Sample size depends on;
– Total number of negatives slides processed
each year.
– Slide positivity rate.
– Expected performance (sensitivity and
specificity) compared to the controllers.
– Maximum number of errors allowed before
action is taken.
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Summary
 Establishment of a Laboratory network is an
important function of a National level Program
Manager
 Internal Quality Control and External Quality
Assurance are essential for ensuring proper
diagnosis by sputum smear microscopy
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