The approach to diagnosing TB in children and adolescents living with HIV is essentially the same as diagnosing TB in HIV-negative children (see Chapter 4). Diagnosis of TB in children and adolescents living with HIV can be more challenging than in HIV-negative children, however (6):
- Clinical features consistent with PTB are common in children and adolescents living with HIV but may be caused by other diseases and therefore lack specificity for a diagnosis of TB.
- Most children living with HIV have been infected via mother-to-child transmission. The peak age prevalence for HIV is under 5 years. This is also the age group in which it is most difficult to confirm the cause of acute or chronic lung disease, including TB.
- TST is less sensitive in children and adolescents living with HIV than in HIV-negative children and adolescents. Induration of >5 mm is considered positive if the child is living with HIV (see Annex 2).
- Children and adolescents living with HIV have a very high incidence of acute and chronic lung diseases other than TB.
- Children and adolescents living with HIV may have lung disease of more than one single cause (coinfection), which can mask response to therapy.
- There is an overlap of radiographic findings in TB and other HIV-related lung diseases.
The integrated treatment decision algorithms for the diagnosis of PTB in Chapter 4 may be used in children living with HIV aged under 10 years. In these algorithms, children living with HIV are regarded as having a relatively high risk for TB when they present with symptoms of PTB, and the steps applicable to the high-risk group should be used. As with all children with presumptive PTB, every attempt should be made to confirm the diagnosis by conducting mWRDs on suitable specimens, including stool, nasopharyngeal aspirate, (induced) sputum and gastric aspirate (depending on equipment and expertise available). This is especially important for children living with HIV who are contacts of people with confirmed DR-TB.
LF-LAM is an important additional diagnostic test in children and adolescents living with HIV. Urine LF-LAM is an immunocapture assay based on the detection of the mycobacterial lipoarabinomannan antigen in urine. This is a potential point-of-care test for certain populations being evaluated for TB. Although the assay lacks sensitivity, it can be used as a fast bedside rule-in test for people living with HIV, including children and adolescents, especially in urgent cases where a rapid TB diagnosis is critical for the person’s survival. The Alere Determine TB LAM Ag is the only commercially available urine LF-LAM test endorsed by WHO (76).
All children and adolescents living with HIV with signs and symptoms of PTB should have at least one specimen (stool, NPA, sputum or gastric aspirate in children; sputum in adolescents) submitted for an mWRD assay if possible. Results of LF-LAM, with a test time of less than 15 minutes, are likely to be available before mWRD results. Treatment decisions should be based on the LF-LAM result while awaiting the results of other diagnostic tests. LF-LAM should be used as an add-on to clinical judgement in combination with other tests (see Box 4.4 in Chapter 4). LF-LAM should not be used as a replacement or triage test. A positive LF-LAM is regarded as bacteriological confirmation of TB (76).
For children living with HIV with signs and symptoms of EPTB, the guidance in Chapter 4 applies as well.