Xpert MTB/RIF and TrueNat can rapidly and accurately diagnose TB and rifampicin resistance from sputum samples. LF-LAM has limited use for diagnosing TB in people living with HIV who have low CD4 counts or are seriously ill. While various diagnostic tools are available, quality sputum samples and proper testing procedures are essential for effective TB case detection and treatment.

1. MOH HIV/TB ECHO
Laboratory TB Case Detection
20 March 2023
Judith Mzyece

2. Learning Objectives
1. Know the different diagnostic tools within
the TB programme’s diagnostic network
2. Interpret diagnostic results appropriately
The speaker has no significant financial conflicts of interest to disclose.

3. Poll Question 1
All of the following are barriers to accessing TB
diagnosis and treatment except
a) Early return of Xpert results
b) Poor specimen transport
c) Inefficient linkage of the patient to medical care
d) Services provided by private sector health care
providers not following national guidelines

4. Overview
To treat a person with TB infection or disease, one must
first find and diagnose them
An estimated 16% of cases of active TB disease went
undetected in 2021
This means that an estimated 10,000 went without
proper TB care in 2021, leaving them ill and at risk of
death and with potential to transmit disease to others

5. Laboratory diagnosis of TB contd
Diagnostic services for all forms of TB such as
EPTB, Childhood TB, HIV-TB and DR TB are
available under the programme
Closing the undetected gap requires much
better use of the tools available

6. Challenges
to access
to
Diagnosis
and
treatment
Delays for diagnosing and
treating TB due to:
1. Delayed return of results Poor
specimen transport.
2. Inefficient linkage of the patient
to medical care
3. Services provided by private
sector health care providers not
following national guidelines

7. Poll Question 2
• Which of these tests is recommended
for initial diagnosis of TB
a) Smear Microscopy
b) TB Lamp
c) LAM
d) Xpert MTB/RIF and TrueNat
e) LPA
f) Culture

8. APPROVED TB
DIAGNOSTIC TOOLS
AVAILABLE IN ZAMBIA

9. Microscopy
(> 100 years ago)
• Inexpensive
• Simple
• Poor sensitivity (20 – 60%)
• (10,000 bacilli/ml of sputum)
• False negatives and missed TB
cases

10. Role of Smear Microscopy
• Smear positive patients are up to ten times
more likely to be infectious than smear
negative patients
• The purpose of sputum microscopy is to:
1. Diagnose people with infectious TB
2. Monitor the progress of treatment
3. Confirm that cure has been achieved
10

11. Xpert MTB/RIF
Advantages
• High sensitivity
• 200 bacilli/ml of sputum
• Automated
Disadvantages
• High equipment
maintenance cost
• Air conditioning and dust
free rooms
• Cost 10 USD per test

12. Xpert MTB/RIF
• A single sputum sample is
recommended for Xpert MTB/RIF
• An additional sputum sample is
needed in case of an
error/invalid/no result and
Indeterminate result
• Additional samples should be
collected for culture/DST
depending on the Rifampicin
Resistance result

13. Interpretation of Xpert
MTB/RIF results
Report ‘MTB not detected’ or
MTB detected with grading
– For rifampicin resistance results
report ‘ Rif resistance not
detected’ or ‘Rif resistance
detected’.
– Error/invalid/no result results
report ‘please submit a new
specimen’

14. Interpretation of Xpert
MTB/RIF results
• Results must be recorded in
the TB lab register and
presumptive TB register
• Use red ink for positive
results
• Reports must be submitted
within the TAT

15. Poll Question 3
LF- LAM can be used alone to diagnose
TB in the following population
a) Children
b) HIV population
c) Adults regardless of HIV status
d) None of the above

16. Urine LAM

17. LF-LAM
Advantages
Sample is easy to obtain
Rapid dip stick test takes 25 minutes to
get results
Simple
Inexpensive
Assists in detecting TB in PLHIV with low
CD4 cell counts or who are seriously ill

18. LF-LAM
Disadvantages
Low sensitivity (56%) in people living with HIV who are seriously ill with TB
symptoms, and suboptimal specificity.
Cannot tell about drug susceptibility
Can only be used in a specific population with low CD4 cell count and who are
seriously ill (low specificity in HIV-negative populations)
Cannot differentiate MTB from non-tuberculous mycobacteria (NTM)
A negative result should be followed up with another kind of test to rule out TB

19. KEY MESSAGE
19
LAM IS NOT A
REPLACEMENT FOR
RAPID MOLECULAR
DIAGNOSTIC TESTS
LAM SHOULD BE USED
FOR DIAGNOSIS IN
RECOMMENDED PATIENT
GROUPS
LAM SHOULD BE USED
FOR DIAGNOSIS ONLY
AND NOT FOR
TREATMENT MONITORING

20. TB- LAMP Assay
• High sensitivity
• Manual
• Low equipment
maintenance cost

21. TB- LAMP Assay
• Used as a replacement for smear microscopy
for the diagnosis of pulmonary TB in adults
with signs and symptoms
• It can also be used as a follow-on test to
smear microscopy when further testing of
smear negative specimen is necessary
• It can differentiate between MTBC and other
species of mycobacteria

22. TrueNat
Is a portable, battery-operated device to
rapidly detect MTBC and rifampicin
resistance
WHO recommends the use of TrueNat
TB test as the initial diagnostic test
rather than microscopy
It will be in the country soon after
method validation is completed

23. Laboratory investigations for Drug
resistance
• Patients with MTB Detected Rif Detected must
have samples collected and sent for DST.
• LPA is recommended for rapid detection of
resistance to RIF, INH, FQs and
aminoglycosides
• Phenotypic DST remains the most accurate
way to diagnose DR-TB (gold standard)
• Culture should be used for monitoring
treatment for drug resistant TB

24. SUMMARY

25. Xpert MTB/RIF and TrueNat can rapidly
and accurately diagnose TB and RR
Collection of good quality sputum is
essential
Risk assessment is an important step
LF-LAM does not identify resistance
Alere LF-LAM should always be used
according to the algorithm
Summary on the diagnostic tools

26. Methods for DR-TB diagnosis can be
phenotypic or genotypic
Patients who need DST will be identified
by the various levels or facilities treating
DR-TB
Xpert MTB/RIF is recommended for EPTB
diagnosis in selected samples, including
from lymph node, CSF and tissues.
Stool testing on Xpert MTB/RIF is used
where Gastric lavage can not be
collected
Summary on the diagnostic tools

27. Summary on the
diagnostic tools
• Methods for DR-TB diagnosis
can be phenotypic or
genotypic
• Patients who need DST will
be identified by the various
levels or facilities treating
DR-TB

28. Summary on the
diagnostic tools
• Xpert MTB/RIF is
recommended for EPTB
diagnosis in selected
samples, including from
lymph node, CSF and tissues.
• Stool testing on Xpert
MTB/RIF is used where
Gastric lavage can not be
collected

29. TB case detection
29
Early detection of bacteriologically PTB should be
a priority for every health facility.
Early detection and treatment of these cases limits
the destruction of the lungs and limits
infectiousness
Health workers either fail to consider TB or the
examination of sputum is delayed or not
performed at all

30. The use of Presumptive TB Register
and lab TB Register
• The presumptive TB Register is a record of;
o All Presumptive TB patients at the health facility and
o Their sputum samples sent to the laboratory
• Particularly useful for monitoring whether results are
returned for all sputum samples sent to the laboratory
• Also helpful for monitoring case detection activities of the
health facility
Similarly, laboratory TB Register is useful for tracking lab
results and monitoring case detection
30

31. Sputum sample Referral
• Pack the sputum containers in a box (preferably cooler box with ice packs)
• Enclose a Request form for Sputum Examination for each patient
• Total time from collection until reaching laboratory should be as follows;
o For culture: Where there is no fridge, do not keep for more than 3
days).
o Where there is a fridge: (Store between 2 to 8 degrees Celsius and do
not keep for more than 5 days).
o Xpert MTB/RIF : Do not keep the specimen at 2-8C for more than 10
days and room temperature for 72 hours.
31

32. Sputum samples for referral
32
Keep samples in 1) refrigerator, or 2) cool place or
3) room with temp <24˚C, 4) away from direct
sunlight, until transportation
Where possible, fix the slides then send to the lab
NB: It's recommended that sputum samples for
referral is kept between 2 to 8 degrees Celsius

33. Summary of Key Points
LF – LAM is an add on
test and should never
be conducted without
Xpert MTB/RIF or X-ray
Good quality sputum
sample should always
be collected
All Xpert MTB detected
results should be
accompanied with the
grading e.g low,trace etc
Peripheral facilities that
do not perform Xpert
MTB/RIF testing should
refer samples and not
patients for testing.

34. References
1. National TB and Leprosy Programme Consolidated
Tuberculosis guidelines
2. https://birac.nic.in/product-detail.php?product=46
3. https://www.thelancet.com/journals/laninf/article/PIIS1473-
3099%2811%2970251-1/fulltext
4. https://www.cepheid.com/en/systems/GeneXpert-Family-of-
Systems/GeneXpert-System

35. Poll Question 1
All of the following are barriers to accessing TB
diagnosis and treatment except
a) Early return of Xpert results
b) Poor specimen transport
c) Inefficient linkage of the patient to medical care
d) Services provided by private sector health care
providers not following national guidelines

36. Poll Question 1
All of the following are barriers to accessing TB
diagnosis and treatment except
a) Early return of Xpert results
b) Poor specimen transport
c) Inefficient linkage of the patient to medical care
d) Services provided by private sector health care
providers not following national guidelines

37. Poll Question 2
Which of these tests is recommended
for initial diagnosis of TB
a) Smear Microscopy
b) TB Lamp
c) LAM
d) Xpert MTB/RIF and TrueNat
e) LPA
f) Culture

38. Poll Question 2
Which of these tests is recommended
for initial diagnosis of TB
a) Smear Microscopy
b) TB Lamp
c) LAM
d) Xpert MTB/RIF and TrueNat
e) LPA
f) Culture

39. Poll Question 3
LF- LAM can be used alone to diagnose
TB in the following population
a) Children
b) HIV population
c) Adults regardless of HIV status
d) None of the above

40. Poll Question 3
LF- LAM can be used alone to diagnose
TB in the following population
a) Children
b) HIV population
c) Adults regardless of HIV status
d) None of the above