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Internal Quality Control (QC) and External Quality Assessment (EQA) for M. tuberculosis Testing. John Ridderhof, DrPH. Division of Laboratory Systems/PHPPO Centers for Disease Control and Prevention. TB Testing Services in LIFE Countries. Direct AFB smear microscopy Case detection

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Internal Quality Control (QC) and External Quality Assessment (EQA) for

M. tuberculosis Testing

John Ridderhof, DrPH

Division of Laboratory Systems/PHPPO

Centers for Disease Control and Prevention


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TB Testing Services in LIFE Countries Assessment (EQA) for

  • Direct AFB smear microscopy

    • Case detection

    • Monitoring treatment

  • Culture and Drug susceptibility testing (DST)

    • Surveillance

    • Assess treatment failures

    • Smear negative diagnosis?

  • Other — Nucleic acid amplification tests


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The Keys to successful Quality Control are: Assessment (EQA) for

  • Adequately trained, interested, and committed staff

  • Common sense use of practical procedures

  • A willingness to admit and rectify mistakes

  • Effective communication

    Ref: Laboratory Services in Tuberculosis Control, WHO


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Culture and DST Assessment (EQA) for Specimen Collection

  • In most countries specimen collection is a laboratory responsibility


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Culture and DST Assessment (EQA) for Specimen Viability

  • Sputum should not be stored at room temperature for longer than 3 days for culture

  • Can be stored up to 4 weeks without loss of smear positivity—but not recommended to to loss of ability to fix smear

Paramasivan CN et al, Tubercle 1983 64(2) 119-24


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Variables Affecting the Quality of Culture Assessment (EQA) for

  • Quality of specimen (sputum versus saliva)

  • Transport time and conditions

  • Digestion/decontamination of specimen

    • Method — Petroff, NALC/NaOH

    • Centrifugation — sufficient G-force

    • Technique — timing, use of vortex, decanting


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QC of Culture Monitors Assessment (EQA) for

  • Contamination rate (2% - 5%)

  • Correlation between smear and culture

    • Percentage of culture isolates from smear positive specimens

  • Isolation rate for saprophytic nontuberculous mycobacteria (NTM, e.g. M. gordonae)


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What’s the problem? Assessment (EQA) for Correlation of Smear and Culture

Culture

Smear


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QC indicators for DST Assessment (EQA) for

  • Weekly drug-susceptible control strain

  • Drug resistant control strains?

    • New culture media and drugs

  • Internal comparison of methods if more than one method is available

  • Exchange isolates with supranational laboratory


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External Quality Assessment Assessment (EQA) for Culture

  • College of American Pathologists

    • 10 samples/yr, 10 isolation and identification, 2 DST, 2 AFB smears

  • Other Proficiency testing programs

    • NEQAS (UK)

    • South Africa Medical Research Council


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External Quality Assessment -- DST Assessment (EQA) for WHO/IUATLD Supranational Network

  • Required as part of WHO surveillance for drug resistance

  • 23 supranational laboratories

    • Supranational laboratories receive 20 cultures/yr for assessing performance

  • >50 national or regional laboratories

    • National laboratories share a sample of cultures with supranational laboratory to compare performance


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External Quality Assessment Assessment (EQA) for Drug Susceptibility Testing-M.tb

  • CDC Performance Evaluation Program

  • M. tuberculosis and NTM drug susceptibility

    • 150 Laboratories; 17 International

    • 10 cultures/yr; 6 M.tb, 4 NTM


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Direct AFB Microscopy Assessment (EQA) for

  • Internal Quality Control

  • External Quality Assessment (EQA)

    • onsite evaluation

    • rechecking

    • proficiency testing


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Internal Quality Control Assessment (EQA) for For AFB Microscopy

  • Microscope

    • preventative maintenance

    • routine cleaning

  • Stains

    • expiration dates stains and chemicals

  • Staining

    • positive and negative controls


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Proposed International Guidelines Assessment (EQA) for EQA – AFB Microscopy

  • Co-sponsored by WHO, IUATLD, KNCV, APHL, and CDC

  • Consensus of 15 member workgroup including representatives from LIFE countries — Uganda, Senegal, South Africa, and India


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EQA -- AFB Microscopy Assessment (EQA) for On-site Evaluation -- Background

  • Most countries lack the resources for annual visits of peripheral laboratory by central laboratory staff

  • Laboratories in most countries are visited by a non-laboratory District supervisor

  • Optimum evaluation is performed by trained laboratory staff in supervisory role


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On-site Evaluation Results - Uganda Assessment (EQA) for

BEFORE

AFTER

Aziz, M. and G. Bretzel, Unpublished Data


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EQA - AFB Microscopy Assessment (EQA) for Rechecking - Background

  • Recommended by IUATLD and WHO

  • Usually 100% of positive and 10% of negative smears

  • Usually unblinded — adds bias*

  • Reviews patient testing; including smear preparation, staining, and interpretation

    *Lan N.T.N. et al, 1999 Int J Tuberc Lung Dis 3(1): 55-61


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Rechecking Slides in Mexico 1998 Assessment (EQA) for

  • States provided data for 438 of 637 laboratories

  • Only 303 laboratories had complete and consistent data

  • Only 109/303 (36%) had any FN or FP error

  • 194 (64%) laboratories with no errors had 55% of total test volume — so presence of errors was not dependent on volume


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EQA - AFB Microscopy Assessment (EQA) for Proficiency Testing - Background

  • Uncommon in resource-limited countries

  • Prepared smears (South Africa) or patient slides (Senegal) sent from central laboratory

  • Consistent challenge of laboratory test performance

  • PT test performance may be different from testing routine patient specimens


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PT Implementation in Mexico Assessment (EQA) for

  • Inspected 587 of 637 laboratories

  • 604 microscopists given a 2 hour, 10 slide test

    • 52% had score >80

    • 33% had score 60-79

    • 15% had score <60

  • 536/604 (88.7%) finished all 10 slides

  • 216 persons with score <80 received training followed by second PT: average scores improved from 61 to 90 (P-value < 0.0001).


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Proposed International Guidelines Assessment (EQA) for EQA - AFB Microscopy Components

  • Resource analysis to determine appropriate EQA

  • Checklists for onsite evaluation by non-laboratory district supervisor or supervising laboratory staff

  • Blinded rechecking using a random statistical sample from each laboratory

  • Procedures to develop PT slides

  • Sample forms


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Proposed EQA - AFB Microscopy Guidelines Assessment (EQA) for Key FeaturesResource Analysis

  • Inventory available resources (actual/projected)

    • Manpower, supplies, communication, administrative, financial

  • Examine effectiveness of current EQA activities

  • Gather laboratory service information

  • Planning—options for the evolution of EQA

  • Pilot test and document changes

  • Expansion based on availability of resources


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Proposed EQA – AFB Microscopy Guidelines Assessment (EQA) for Resource AnalysisPhased Approach

  • Assure the five elements of DOTS

  • Develop a central reference and intermediate laboratories to carry out EQA

  • Determine the existing capacity for EQA

  • Train district health officials to evaluate the minimal functions of microscopy laboratories


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Proposed EQA – AFB Microscopy Guidelines Assessment (EQA) for Resource AnalysisPhased Approach (cont)

  • Proficiency testing to evaluate performance

  • Pilot rechecking program

  • Determine resources: additional PT or phased implementation of rechecking


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Proposed EQA – AFB Microscopy Guidelines Assessment (EQA) for Key FeaturesOn-site Evaluation

  • Develop a standard checklist of questions and indicators

  • Include minimal evaluation that can be performed by non-laboratory trained personnel (e.g., inventory supplies, reagents, equipment)

  • Include detailed evaluation that can be performed by supervisory laboratory staff

  • Train laboratory and non laboratory staff to assure consistent application


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On-site Evaluation Performed by Assessment (EQA) for Non-laboratory Staff Examples:

  • Are all staining reagents available and within expiration dates?

  • How are wire loops cleaned?

  • Is the laboratory register present and all columns completed properly?

  • How is maintenance on the microscope performed?


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On-site Evaluation Performed by Assessment (EQA) for Laboratory Staff Examples:

  • Does the technician verify that the container is properly labeled?

  • How are slides labeled?

  • How often is the carbol fuchsin filtered?

  • How many fields are examined to report a negative smear?


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Proposed EQA – AFB Microscopy Guidelines Assessment (EQA) for Key FeaturesProficiency Testing

  • Laboratory may re-use patient slides but a procedure is provided to produce test slides for consistent slide sets

  • Recommended slide set is 10 slides: 5 stained and 5 unstained

  • Simple forms for slide production and collection of test results


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Proposed EQA – AFB Microscopy Guidelines Assessment (EQA) for Key FeaturesRechecking

  • Emphasizes “blinding” and random sample using the laboratory register

  • Sample size is based on Lot Quality Assurance Sampling (LQAS) with parameters selected for test volume and desired specificity

  • Positives and negatives sampled

  • Minor errors (FP or FN with 1-9 AFB/ 100 f) are used as a surrogate


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Semi-quantitative Reporting Assessment (EQA) for Ziehl Neelsen

  • No AFB are found in 100 fields:

    “No acid-fast bacilli observed.”

  • 1-9 /100 fields: Report the exact figure.

  • 10-99 AFB /100 fields, 1+

  • 1-10AFB /field, 2+

  • Greater than 10 AFB/ field, 3+


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Rechecking Assessment (EQA) for LQAS example -Mexico



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Some Reasons for Assessment (EQA) for False Positive Results:

  • Errors in specimen handling or recording information

  • Re-use of containers or positive slides

  • Unfiltered fuchsin

  • Contaminated immersion oil

  • Inadequate decolorization


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Some Reasons for Assessment (EQA) for False Negative Results:


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Some Reasons for Assessment (EQA) for False Negative Results:

  • Errors in specimen handling or recording information

  • Poor quality sputum

  • Excessive decolorization

  • Reading less than 100 microscopic fields


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