Because of their increased risk for TB, children aged under 10 years living with HIV should be screened for TB at every encounter with a HCW, with the following screen: cough, fever, poor weight gain or close contact with a person with TB (see Chapter 2 on screening). For recommendations on screening tools for adolescents aged 10–19 years living with HIV, see Box 2.7 in Chapter 2 (13).
Positive or abnormal screening tests identify children and adolescents living with HIV who have a higher probability of TB disease and should be referred for diagnostic evaluation (see Section 7.1.4 and Chapter 4). People with normal or negative screening tests or algorithm results should be referred for evaluation for TPT (see Section 7.1.3 and Chapter 3).
W4SS (current cough, fever, weight loss and night sweats) is a simple non-invasive screening approach that does not require infrastructure (technology, electricity, internet) and is feasible to implement in any setting. The results of a symptom screening are subjective, however, and depend on the patient’s level of understanding and willingness to share their physical experience of symptoms, and on the provider’s interpretation of the patient’s self-reported symptoms. The quality and consistency of W4SS, therefore, are likely to vary among clinical settings.
The evidence review conducted for the 2021 TB screening guidelines showed that W4SS has relatively high sensitivity (83%) but low specificity (38%) in adults and adolescents living with HIV. The sensitivity of W4SS among outpatients on ART is relatively low (53%), indicating that W4SS alone would not be sufficient to detect TB among people receiving regular ART care. Despite these limitations, W4SS is an essential part of the clinical examination of most subpopulations and is the most accessible screening tool at all levels of the health system. It can be repeated as often as necessary, with more intense screening strategies used less frequently, such as at annual check-ups.
Familiarity with W4SS is widespread in many HIV services as a result of capacity-building and supervision. It also has an important role in ruling out TB disease due to its high negative predictive value in most settings, which is important to identify people living with HIV who would benefit from TPT in the absence of TB disease (13).
CRP is an indicator of systemic inflammation that can be measured with a blood test. A point-of-care fingerprick test is available, making it simple, affordable and feasible in primary care. The turnaround time from testing to receiving the result with many CRP test kits is 3–5 minutes, allowing a quick clinical decision to refer a patient for diagnostic evaluation for TB disease or initiation of TPT. An additional potential benefit of CRP is that it can alert clinicians to the presence of other diseases, such as bacterial pneumonia, bronchitis, and other infectious and non-infectious conditions (e.g. lymphoma). Data reviewed for the 2021 screening guideline revision support sequential combination of a positive W4SS followed by CRP with a cut-off of >5 mg/L, particularly for people not on ART. CRP can also play an important role in ruling out TB disease before initiation of TPT (13).
CXR is useful for screening people living with HIV for TB. It is currently recommended by WHO for use in parallel with W4SS for ruling out TB disease before initiating TPT. Similarly, CXR can be used in parallel with W4SS to screen for TB disease, with a positive or abnormal result on either CXR or W4SS indicating the need for further diagnostic evaluation. “Any abnormality” or “abnormality suggestive of TB” on CXR can be used, depending on the context, availability of radiological expertise and resources, and a preference for higher sensitivity or higher specificity (13).
Further details on these screening tools, their accuracy and considerations for their use in adolescents living with HIV are described in Chapter 5 of the WHO operational handbook on tuberculosis. Module 2: screening – systematic screening for tuberculosis disease (13).