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Genital Tuberculosis: Is It All
Circumstantial?
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Why has this Q been asked?
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In clinical practice we do not have an easy answer
to lab diagnosis of genital TB
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On most occasions we tend to make a presumptive
diagnosis and start the treatment
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TB is a classic case where the treatment is used
to prove the diagnosis
My reply to the Q: Is
It All Circumstantial is Yes and No!
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This diagnostic dilemma arises because of varied
clinical presentations, diverse results on imaging and endoscopy
and a mixed bag of bacteriological and serological tests. Hence
genital tuberculosis is a diagnosis based on the collective
evidence from all these
Routine clinical
scenario
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Mrs A, 25 yrs nulligravida wants solution of her
primary infertility of 4 years
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Her M/H is regular
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She has no past history of TB (in most cases this
is true)
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Her G/E is non contributory
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Gyne Examination reveals normal size uterus with
restricted mobility
Blood routine
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Non-contributory except for the ESR being 56
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Does this in any way lead you to genital
tuberculosis?
ESR
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Very non-specific investigation
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Used previously for suspecting TB
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Now used for prognostication and judging the
treatment response
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No other role
She is subjected to
pelvic USG: Non-contributory
Pelvic ultrasound, a
useful initial screening test, was able to identify In subjects
with known genital tuberculosis:
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Ascites/ loculated fluid (100%),
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Adnexal mass (93%),
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Peritoneal thickening(69%),
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Omental thickening(61%), and
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Endometrial involvement (83%)
If at this stage on any
of these findings a genital pelvic TB is labeled: It is indeed
Circumstantial
Review of her past
investigations revealed an HSG plate
Chauhan reported
genital TB in 7.5% of hysterosalpingography performed for
infertility.
In their series, the
most common feature was Isthmic-ampullary tubal occlusion in 81%
cases With terminal hydrosalpinx in 16% cases and The uterus
affected by scarring, irregular outline and intravasations in
27% cases,
HSG
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This imaging technique became so over-hyped that
orations were delivered on use of HSG in diagnosis of female
genital tract TB
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But we all know how circumstantial it was
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We respect the practice at that time as competent
modalities were limited or nonexistent
X-ray chest
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In view of this HSG picture she was subjected to
X-ray chest which was normal
She was therefore taken
up for endoscopy work-up
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Endoscopy has the dual advantage of pelvic organ
visualization and sample collection from inaccessible sites for
laboratory diagnosis.
The fallopian tubes are
almost universally affected, as evidenced by
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Complete tubal block in
80%,
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Adhesions and calcifications in 43%,
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Adherent mass in
35.8%,
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Nodular sclerosis in
11.7%, and
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Miliary tubercles and ascites in 9.4% cases of
genital TB
She was also subjected
to hysteroscopy
Diagnostic hysteroscopy
allows visualization of
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Tubercles,
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Microcaseation,
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Distorted ostium,
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Synechia, and
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Outpouching in the endometrial cavity.
Biopsy may also be
taken from suspicious sites.
Search for M.
Tuberculosis continues
A saline wash matter
was taken from the pelvic cavity for further investigations. The
suspicious lesion was biopsied on hysteroscopy
How should the material
be sent?
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Material for laboratory diagnosis should be
collected with two objectives, histology and culture, and the
tissue should be divided into two equal parts. One part should
be sent as per routine laboratory requirements in a fixative
solution (formalin or Bouin’s fluid).
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The other part for culture should be collected in
a sterile container
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Bacterial overgrowth should be prevented by
storing it at a temperature of 40 to 80C.
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Direct inoculation on the culture medium at the
site of collection itself has also been described.
On staining for AFB two
possibilities: AFB +ve or - ve
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AFB +ve: Not definitive – could be Non
Mycobacterial Tuberculosis organisms
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AFB -ve: Doesn’t rule out, Number of the organisms
may be very few, If so: GROW THEM (culture them!)
AFB Smear (Z.N. Stain)
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It was negative
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If it was positive it could have become nearly
definitive and the circumstantial circuit would have ended
What
about the good old HxP Histopathology
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A histological diagnosis used to be made with
traditional HE staining as well as with ZN staining with a basic
fuschin dye.
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The classic features are caseous necrosis,
giant cells, epithelial cell clusters and lymphocyte
infiltration.
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Lesions are highly indicative of but not exclusive
to TB unless tubercle bacilli are seen.
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BUT a similar picture may also be seen in fungal
or sarcoid disease
HP report showed
caseous necrosis, giant cells, epithelial cell clusters and
lymphocyte infiltration – Does this clinch the issue? Not
necessarily! Lesions are highly indicative of but not
exclusive to TB unless tubercle bacilli are seen. A similar
picture may also be seen in fungal or sarcoid disease. If AFB
was positive and HP also positive then this would have ended the
search: it is definitive. As in this patient AFB was negative
and HP indicative it is still circumstantial and matter needs to
be pursued
So the material was
subjected to culture as the search for the illusive AFB
continues because…
AFB
– ve & HP + ve
Poor concentration of AFB in the sample of genital TB
OR
AFB
– ve & HP + ve
fungal or sarcoid disease
AFB Culture
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Higher sensitivity than AFB
smears.
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Culture methods are still the gold standard in the
detection of genital TB.
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Helps in exact identification
of Mycobacterium and putting up drug sensitivity.
Culture
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Culture is traditionally performed on solid egg or
agar based media such as Lowenstein Jenson (LJ) or Middlebrook
THIO and microinoculated at 37°C under 5% CO2.
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Growth is detected after 4-5 weeks. Colonies
are seen if the bacillary count is more than 1000 bacilli. This
improves the sensitivity as compared to ZN staining alone which
requires 10,000 bacilli to be positive
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However improvements in media have allowed
colonies to grow even when the count is 100 bacilli
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This is possible with the use of liquid based
media radiometric growth detection such as BACTEC 460 or
non-radiometric CO2 growth detection with BACTEC
ALERT 3 D
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This assay system is based on generation of
radioactive carbon dioxide from substrate palmitic acid.
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This method has been extensively used all over the
world and Growth can be detected in 5-10 days in this system.
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Inclusion of NAP (beta nitro alpha acetyl amine
beta hydroxypropiophenone) can help in distinguishing M.
TUBERCULOSIS (inhibited) from other mycobacteria.
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This system has been widely used for drug
susceptibility testing and is currently used as a comparative
standard
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BACTEC has a sensitivity of 80- 90%
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LJ medium has a sensitivity of only 30- 35%.
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This high sensitivity is particularly useful in
cases of genital TB as traditional methods show poor recovery of
acid fast bacilli
BACTEC report in this
patient
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Showed AFB organisms POSITIVE
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Does this mean we are beyond circumstantial now
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Yes, this is nearly definitive
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The last frontier is to identify that these AFBs
are M. TB
AFB Identification
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Possible only after positive
culture.
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Very important to identify
mycobacterium as it may or may not be pathogenic.
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Identification by
bacteriological method has about 60 – 70 % sensitivity
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Identification by molecular
methods has a sensitivity of >90 %
AFB identification by molecular methods
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Two main methods.
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TMA (Thermal
Amplification)
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PCR (Polymerase Chain reaction)
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TMA is RNA based amplification.
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PCR is DNA based amplification.
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TMA is positive only if bacilli
are viable while PCR is positive with both dead and viable
mycobacterium.
PCR
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The polymerase chain reaction is a technique that
shows rapid detection and quantification of few DNA copies with
high sensitivity and specificity.
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Its sensitivity is VERY high
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It requires only < 10 bacteria/ml of specimen
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Rapid method with results available within a day
of the DNA being extracted from the sample.
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It can also be applied to sterile fluids like
peritoneal fluid where the culture is difficult due to a low
bacterial load
Now the combinations
Culture +ve
PCR +ve:
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DEFINITIVE!
Culture +ve
PCR - ve :
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Culture remains the gold standard for diagnosis of
TB
Culture -
PCR - ve :
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Not TB
Typical Clinician’s Question
Can the material could
be subjected straight to molecular method of identification: PCR
?
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The answer is may be!
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But you must be ready to face a very small
possibility of a false positive (lab contamination)
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Fastest and most definitive solution
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PCR in 24 hours and HP report confirming
tuberculous lesion within 3 to 4 days will be a fair compromise
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