DEFINITION, CLINICAL FEATURES AND DIAGNOSIS

A chronic infection caused by Mycobacterium tuberculosis complex. It commonly affects lungs but can affect any organ
(lymph nodes, bones, meninges, abdomen, kidney).

Causes

  • Mycobacterium tuberculosis complex (e.g. M. tuberculosis, M. bovis, M. africanum and M. Microti)
  • Transmission by droplet inhalation (cough from a patient with open pulmonary TB); can also be through drinking
    unpasteurised milk, especially M.bovis

Clinical features

General symptoms

  • Fevers especially in the evening, excessive night sweats
  • Weight loss and loss of appetite

Pulmonary TB

  • Chronic cough of >2 weeks (however, in HIV settings, cough of any duration)
  • Chest pain, purulent sputum occasionally blood-stained, shortness of breath

Extrapulmonary TB

  • Lymphnode TB: Localized enlargement of lymph nodes depending on the site affected (commonly neck)
  • Pleural or pericardial effusion
  • Abdominal TB: ascites and abdominal pain
  • TB meningitis: subacute meningitis (headache, alteration of consciousness)
  • Bone or joint TB: swelling and deformity

omplications

  • Massive haemoptysis – coughing up >250 mL blood per episode
  • Spontaneous pneumothorax and pleural effusion
  • TB pericarditis, TB meningitis, TB peritonitis
  • Bone TB: can be TB spine with gibbus, TB joints with deformity)
  • Respiratory failure

TB Case Definitions

CASE DEFINITION DESCRIPTION
Presumptive TB
patient
Any patient who presents with
symptoms and signs suggestive of TB
(previously called a TB suspect)
Bacteriologically
confirmed TB
patient
Patient in whom biological specimen
is positive by smear microscopy,
culture, Xpert MTB/RIF. All such
cases should be notified (registered in
the unit TB register)
Clinically
diagnosed TB
patient
Patient who does not fulfil the criteria
for bacteriological confirmation
but has been diagnosed with active
TB by a clinician or other medical
practitioner on the basis of clinical
symptoms and other investigations

Classification of TB Infection

CRITERIA CLASSIFICATION
Site of the
disease

Pulmonary TB
: bacteriologically
confirmed or clinically diagnosed
case, affecting lung parechyma or
tracheobronchial tree. Isolated TB
pleural effusion and mediastinal
lymphadenopathy without lung
tissue involvement is considered
extrapulmonary TB

Extrapulmonary TB
: any other case
of TB. If the patient has pulmonary
and extrapulmonary involvement, he/
she will be classified as pulmonary
History of
treatment

New:
no previous TB treatment (or
treatment less < 1 month)

Relapse
: patient who completed
a previous course of treatment,
was declared cured or treatment
completed, and is now diagnosed with
a recurrent episode of TB

Treatment after failure
: those who
have previously been treated for TB
and whose treatment failed at the
end of their most recent course of
treatment

Treatment after loss to followup
patients
: have previously been
treated for TB and were declared lost
to follow-up at the end of their most
recent course of treatment. (These
were previously known as treatment
after default patients)

Other previously treated patients

are those who have previously
been treated for TB but whose
Outcome after their most recent
course of treatment is unknown or
undocumented
HIV status Positive: patients who tested HIV
positive at time of diagnosis or
already enrolled in HIV care

Negative
: patients who tested
negative at the moment of diagnosis

Unknown
. If testing is then performed
at any moment during treatment,
patient should be re classified
Drug resistance
(based on drug
susceptibility
Tests)

Rifampicin resistant
: any case of
rifampicin resistance (isolated or in
combination with other resistance)
(RR-TB)

Monoresistant
: resistant to only one
first line anti-TB drug

Poly drug resistant
: resistant to
more than one first line anti TB other
than both rifampicin and isoniazid

Multi drug resistant
: resistant to
rifampicin and isoniazid (MDR –TB)

Extensive drug resistance
: resistant
to rifampicin, isoniazid and any
fluoroquinolone and at least one of
the 3 second line injectable drugs
(capreomycin, kanamycin, amikacin)
(XDR-TB).

Differential diagnosis

  • Histoplasma pneumonia, trypanosomiasis, brucellosis
  • HIV/AIDS
  • Malignancy
  • COPD, asthma, bronchectasis, emphysema etc
  • Fungal infection of the lungs e.g. Aspergillosis

Investigations for TB Infection

  • Sputum smear microscopy for AAFBs (ZN stain),
    • one spot and one early morning sample. If one is positive, it is diagnostic for pulmonary TB. This test is widely
      available in many facilities with a laboratory.
    • Sputum samples for children can be collected by inducing sputum using sputum induction kits
  • GeneXpert MTB/Rif: automated DNA test on body samples (sputum, lymphonodes tissue, pleural fluid, CSF
    etc) which can diagnose pulmonary TB and determine susceptibility to Rifampicin. It is superior to microscopy.

    • Genexpert MTB/Rif should be used as initial test for TB diagnosis among all presumptive TB patients.
    • In facilities with no GeneXpert machines on site, microscopy can be used for TB diagnosis except in
      priority (risk) groups like: HIV positive patients, children < 14 years, pregnant and breastfeeding mothers, health
      workers, contacts with drug resistant TB patients, retreatment cases, patients from prisons or refugee camps,
      diabetics
    • For these priority groups, take a sputum sample and send to a facility with a geneXpert machine through the sample
      referral system (hub system).
  • Other investigations
    • Can be used for sputum and geneXpert negative patients or in case of extrapulmonary TB according to clinical
      judgement (Chest and spine X ray, abdominal ultrasound, biopsies etc)
  • Sputum culture and Drug susceptibility test: is a confirmatory test for TB and also provides resistance
    pattern to TB medicines. Do this test for:

    • Patients with Rifampicin resistance reported with GeneXpert
    • Also patients on first-line treatment who remain positive at 3 months and are reported Rifampicin sensitive on
      GeneXpert
    • Patients suspected to be failing on first-line treatment

    Note: All presumed and diagnosed TB patients should be offered an HIV test