An Early Morning Sputum Sample Is Necessary
for the Diagnosis of Pulmonary Tuberculosis,
Even with more Sensitive Techniques:
Willy Ssengooba
Makerere University Kampala,
Uganda
4/7/2015
Ssengooba, W. et al 2012 Tuberc.
Resear &Treat
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Background: TB in adolescents
• There is scant data on TB among adolescents in Uganda
and worldwide.
• Reports indicate that many adolescents with active TB are
diagnosed during late stage of the disease .
• It is quite challenging to obtain quality sputum samples,
especially in community studies and vaccine trials where
suspects may be identified at early stage of disease.
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Background: sputum samples
• The WHO and IUATLD recommended collection of two sputum
samples for smear microscopy with at least one being an earlymorning (EM).
• Whereas the number and type of sputum samples required for smear
microscopy is well known, the number and type of sputum samples
required for culture have not been well standardized.
• Furthermore, while there is a significant diagnostic gain from EM
sputum samples when using smear microscopy, it is not clear whether
this gain remains significant when using more sensitive techniques
such as culture particularly among adolescents.
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Background ctned
• Objective: to determine the diagnostic yield of the spot
and the incremental diagnostic yield of EM sputum
sample cultures for diagnosis of TB among adolescents in
rural Uganda.
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Methods
Study Design and Setting.
• This study was a sub-component of a large observational
cohort study undertaken by Makerere University School of
Public Health, which enrolled 5000 adolescents in Iganga,
rural Uganda, in preparation for TB vaccine trials ( 20092011).
• The adolescents were assessed for TB at baseline and
followed every 6 months for 1-2 years; and TB suspects
were defined as having TB contact in the household or a
TB symptom for 2 weeks or more.
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Methods ctned
• Sputum samples were obtained daily from the participants
by nurses and transported in cold box (temperature ≤
8◦C) to a reference mycobacteriology laboratory
(biosafety level 3) where culture and analysis were done.
• The analysis included study participants with both EM and
spot sputum samples submitted for culture.
• Laboratory tests included: Smear Microscopy (FM) and
culture ( LJ &MGIT).
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Data analysis
• The primary outcome of our analysis was culture positive TB case,
defined as MTBC positive upon LJ or MGIT culture from either spot
or EM samples.
• Diagnostic yield; referred to the number of TB cases detected by each
sputum sample type (spot or EM) irrespective of whether the
comparator was positive.
• Incremental diagnostic yield; referred to the yield of culture positive
EM samples in terms of TB cases detected when the spot sample from
the same case was negative.
• Used Stata for analysis.
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Study Flow chart
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Results
• Screened 5000, enrolled 2418 participant.
• 1862 participant had both spot and EM samples
• Six (0.3%) were positive by smear microscopy.
• 21 (1.1 %) were culture confirmed MTBC-positive.
• 225 (12.1%) had MOTT on MGIT culture.
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Table 2: Mycobacterial yield from EM and spot sputum samples by different culture
methods (n=1862)
Culture method Results
Spot samples EM samples EM and Total
n (%)
n (%)
spot
n (%)
samples
n (%)
LJ [p< 0.001]
MTBC
1 (0.1)
2 (0.1)
3 (0.2)
6 (0.3)
positive
MOTT
0
0
0
0
Culture
1831 (98.3)
1806 (97.0) 1859
1772 (95.2)
negative
(99.8)
Contaminated 30 (1.61)
54 (2.9)
0
84 (4.5)
MGIT [p<0.001]
MTBC
6 (0.3)
12 (0.6)
3 (0.2)
21 (1.1)
positive
MOTT
106 (5.7)
119 (6.4)
0 (0.0)
225 (12.1)
Culture
380 (20.4)
301 (16.2)
1859
681 (36.6)
negative
(99.8)
Contaminated 436 (23.4)
499 (26.8)
0(0.0)
935 (50.2)
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Results ctned [n=21]
Culture
method
Yield of spot
n (%)
Incremental
diagnostic
yield for EM
(observed)
n (%)
Total number
of
TB cases
detected
n (%)
LJ
4 (19.0)
2 (9.5)
6 (28.6)
MGIT
12 (57.1)
9(42.9)
21 (100)
LJ= Lowenstein Jensen, MGIT= Mycobacterial Growth Indicator
Tube, EM, =Early Morning
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Discussions and conclusion
• EM sample culture has a high incremental diagnostic yield
i.e. 9.5% on LJ and 42.9% on MGIT culture.
• Given the sensitivity of culture one would expect the
incremental gain from EM to be negligible, but it is not.
• MGIT culture gives a higher MTBc yield , but also more
MOTT and contamination.
• More studies to look at the impact of high proportion of
MOTT in a TB vaccine trial perspective are needed.
4/7/2015
Benon B Asiimwe
et al , 2013
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Acknowledgement
Funding:
• EDCTP
• AERAS
• Makerere University /IDI
Co-authors:
• 1(Moses Joloba, Philippa Musoke, Harriet Mayanja-Kizza, James Waako,
Anne Wajja, Benon Asiimwe & Lab team)
• and 2Suzanne Verver
1Makerere
2KNCV
University College of Health Sciences Kampala Uganda
Tuberculosis Foundation, The Netherlands
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4/7/2015