This document discusses how to decipher tuberculosis (TB) laboratory reports. It begins by explaining that labs performing diagnostic testing are regulated by CLIA to ensure quality standards. A typical lab report includes sections for laboratory information, patient information, specimen details, tests performed, and results interpretation. Test results may include AFB smear microscopy, molecular assays for detection of TB and drug resistance, culture outcomes, and antibiotic susceptibility results. Understanding the format and abbreviations used in lab reports is key to interpreting TB test results.

1. Deciphering TB Lab Reports
Jessica Gentry
Tuberculosis Laboratory Supervisor
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2. Laboratory Regulation
Laboratories performing diagnostic testing on human
patient specimens are regulated by CLIA:
Clinical Laboratory Improvement Amendments
Regulations establish quality standards for laboratory
testing performed on specimens from humans, such
as blood, body fluid, and tissue, for the purpose of
diagnosis, prevention or treatment of disease, or
assessment of health.
The purpose is to ensure high-quality testing.
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3. Examples of CLIA regulations:
• Qualified, trained personnel performing testing
• Laboratory inspections/audits
• Enrolled in Proficiency Testing
• Laboratory director overseeing testing
• Written procedures for testing
• Requirements for lab reports
Laboratory Regulation
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4. Lab Reports Are Difficult to Read…
• Different tests performed by different laboratories
• PCR vs. probe vs. NAAT
• Use of abbreviations
• Inconsistent terminology
• Multiple dates—collection date, test date, report date
• Formatting
• Results not listed in chronological order
• Results from multiple laboratories on a single report
• Results moved through a variety of LIMS systems
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5. • Laboratory Information
• Patient Information
• Specimen Information
• Lab Testing Performed
• Results Interpretation
What’s on a Lab Report?
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6. Laboratory Information
• Laboratory Name
• Physical Address
• Laboratory Medical Director
• CLIA Certificate Number
• Referral Laboratory Information
• Department
• Mycobacteriology
• Tuberculosis
• AFB Lab
• Microbiology 6

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9. Patient Information
• Required: Two patient identifiers, typically:
• Patient Name
• Unique Patient Identifier (MRN)
• Date of Birth
• Optional:
• Age
• Gender
• Race/Ethnicity
• Address
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11. Specimen Information
• Specimen Source—sometimes listed as “site”
• Pulmonary (Respiratory): Sputum, bronchial
• Extrapulmonary: Urine, lymph node, CSF, tissue,
etc.
• Descriptive modifiers sometimes added—Induced or
expectorated sputum, tissue location, RUL, etc.
• Collection Date
• Received Date
• Accession Number/Specimen ID/Lab Number
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15. • Test Performed
• Test Result
• Normal vs. Abnormal
• Interpretation
• Units of Measurement
• Qualitative (QL) vs. Quantitative (QN)
• Date Test Reported
Laboratory Tests
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16. AFB Smear Microscopy
• Acid Fast Bacillus (AFB)
• Acid Fast Bacilli, Acid Fast Bacteria
• Digested, Concentrated, or Unconcentrated Smear
• AFB Stain
• Fluorescent
• Fluorochrome
• Auramine O-phenol
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17. AFB Smear Microscopy
AFB Negative
• No Acid Fast Bacilli seen/observed on smear
AFB Positive
• Acid Fast Bacilli seen/observed/found on smear
• <1/field, 1-10/field, >10/field, >50/field
• 1+ (few), 2+, 3+, 4+ (many)
• Rare, Few, Moderate, Many
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21. Molecular Assays
Assays that detect genetic material (DNA) of MTBC:
• Polymerase Chain Reaction (PCR)
• DNA Probe
• MTB-RIF
• Nucleic Acid Amplification Test (NAAT)
• Negative, Not Detected
• Positive, Detected
• Testing can be in the specimen or culture
• Assays can also look for other mycobacteria—M.
avium complex, M. kansasii, M. gordonae
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24. Detection of mutations associated with drug resistance
Assays
• Pyrosequencing
• Sanger Sequencing
• Gene Xpert MTB/RIF
• Whole Genome Sequencing (WGS)
Results
• Detected vs. Not Detected
• Mutation Present vs. Mutation Absent
Molecular Detection of Drug Resistance
Cepheid GeneXpert Cartridge
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28. Culture Results
• AFB culture is typically performed in tandem with an AFB smear
• Test names: AFB Cx, AFB Cx + Stn, AFB Identification (ID)
• Preliminary results may be reported at 2 wks, 4, wks, etc.
• Culture negative—usually reported at 6 wks
• Culture positive
• Organism isolated, Organism ID
• MTBC, MTB, Mycobacterium tuberculosis
• Method used for ID—PCR, probe, MALDI-TOF, etc.
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32. Antibiotic Susceptibility Testing
• Antibiotic tested
• Critical concentration or MIC (Minimum Inhibitory Concentration)
• Sometimes multiple levels per antibiotic
• Result/interpretation
• R=Resistant
• S=Susceptible, Sensitive
• Method used
• Broth (MGIT)
• Agar Proportion (AP)
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36. Conclusions
• Different labs use different test methods
• All labs report results differently
• Labs like to use abbreviations
• BUT—understanding what type of information is
included in a lab report and knowing the keywords
to look for can be very helpful
• ALSO—If you have questions, call the lab and ask!
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37. Questions?
Jessica Gentry
Tuberculosis Laboratory Supervisor
Indiana State Department of Health
jgentry@isdh.in.gov
Phone: (317) 921-5858
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