5.4 Key elements of the diagnosis


Recommendations of how to combine the following elements to arrive at a treatment decision are summarized in the diagnostic algorithms (Section 5.6).

5.4.1 Careful history

– Contact with a known or presumed TB case:
• Timing of the exposure: greater risk if exposure occurred in the past 12 months;
• Closeness of the contact: greater risk if living in same household or sleeping in the same room;
• Type of TB of the source case: greater risk if smear-positive or cavities on X-ray; resistance pattern of the source case.

– Symptoms suggestive of TB:
• Cough persistent for > 2 weeks and not improving;
• Unexplained fever for > 1 week;
• Unexplained weight loss or failure to thrive;
• Unexplained fatigue, lethargy or reduced playfulness.

5.4.2 Clinical examination

– Vital signs: fever and increased respiratory rate may be present.

– Growth: weigh the child and compare with previous records. Weight loss or flattening of the growth curve can signal chronic disease.

– Respiratory examination: abnormal auscultation or percussion may be present. Signs of severe respiratory infection: tachypnoea, cyanosis, hypoxemia (SaO2 < 90%), nasal flaring, chest indrawing, grunting and feeding difficulties in infants.

– Physical signs of EPTB (see also Chapter 2, Section 2.2):

Highly suggestive, e.g.:
• Angular deformity of the spine;
• Cervical lymph node with fistula formation.

Non specific requiring further investigation, e.g.:
• Sub-acute meningitis not responding to antibiotic therapy;
• Distended abdomen with ascites;
• Lymphadenopathy without fistula formation;
• Non-painful enlarged joint.

– Other: certain physical findings may point to alternative diagnoses (e.g. asthma) or relevant co-morbidities (e.g. HIV).

5.4.3 Re-assessment and follow up

The diagnosis is rarely made at the first consultation, as the initial clinical presentation is usually non specific. Follow up is critical to assess if signs and symptoms persist despite a trial of well-monitored non-TB antibiotic treatment.

Particularly suggestive of TB disease are:
– Persistent pneumonia after appropriate, well-monitored antibiotic treatment;
– Measured or reliably reported fever of > 38°C for > 1 week, after common causes such as malaria or pneumonia have been excluded;
– No weight gain despite appropriate nutritional support;
– Persistent or worsening fatigue.

5.4.4 HIV testing

HIV testing should be routinely offered to children with presumed or diagnosed TB.

5.4.5 Diagnostic investigations

The following investigations should be performed in children suspected of TB whenever possible. The unavailability of a test due to resource limitations should not delay the diagnosis of TB.

Tuberculin skin test (TST)

– A positive test can support a diagnosis of TB in a symptomatic child;
– A negative TST does not exclude TB;
– Causes of false positive: BCG, atypical mycobacteria (NTM);
– Causes of false negative: HIV infection, malnutrition.

Chest X-ray

Chest X-ray can be helpful for the diagnosis of intrathoracic TB3. Hilar lymphadenopathy is the most common finding. However, obtaining quality films in children and accurately interpreting them may be difficult. This limits their utility in many settings.

Bacteriology

Try to confirm TB, although treatment should not be delayed if clinically indicated.

For EPTB, obtain specimens from the suspected sites for microscopy and, when possible, for culture, cytology or histopathological examination and molecular methods (e.g. Xpert MTB/RIF).

Bacterial yields are higher in older children, and in children of all ages with severe disease. Two sputum specimens should be obtained: an on-the-spot specimen (at first evaluation), and an early morning specimen. Alternatively, two specimens collected one hour apart are an acceptable option (see Appendix 1).

Xpert MTB/RIF is the initial test of choice in screening for multidrug-resistant TB (MDR-TB). When Xpert MTB/RIF is not available, conventional drug susceptibility test (DST) can be done. DST indications are the same as for adults.