The Conundrum of Cervical Adenopathy

▸ Less than 5 mm and hilar adenopathy. This can signify histoplasma, evolving NTM, or TB. If suspicion for TB is high because of social factors, obtain TST on family members. If family TSTs are negative and still no symptoms are present, then there are two options. First, one could do the serologies and, if they are negative, wait to reapply a TST in 4 weeks. Alternatively, referral for biopsy at this point could more rapidly identify the pathogen.

▸ 5–10 mm in size. Referral for surgical excision is appropriate if the child is not ill, lives where TB prevalence is low, and has no known TB exposure and no BCG vaccination. Excision not only is usually curative, but also provides tissue for microbiologic or histologic diagnosis, rendering serology unnecessary.

I don't agree with the editorial that accompanied this study, in which the author argued for multidrug antimicrobial treatment (Clin. Infect. Dis. 2006;43:1552–4). In my view, unless the position of the node places the facial nerve in jeopardy from excision, surgery is simpler than trying to keep a patient on 3–6 months of multiple, relatively expensive drugs that have potential adverse effects and that children don't like to take. At least one-third of these children either can't tolerate the regimen or don't respond to it, and end up having surgery anyway. The rate of recurrence after surgery is lower, about 5%–8%.

▸ Greater than 10 mm in size. This is generally presumed to be either latent or—if the CXR is positive—active TB. An appropriate TB regimen can be started. Some NTM infections can cause that degree of induration, but these cases are traditionally treated as TB is ruled out. This is possible with node biopsy. Whether to start TB medications before biopsy depends on risk factors.

For this situation, the second article, from Japan, offers future hope for an additional nonsurgical test to reduce the uncertainty about whether the child with a 10-mm or greater induration actually has NTM or TB. The authors evaluated a whole-blood interferon- and enzyme-linked immunosorbent assay (the Quantiferon TB-2G test, made by Cellestis Ltd.) in 50 healthy volunteers, 50 patients with active TB, and 100 patients with known NTM. They also skin-tested each individual (Clin. Infect. Dis. 2006;43:1540–6).

Among the healthy students, TSTs were negative in 64% and the Quantiferon test was negative in 94%. In confirmed TB cases, 64% had greater than 10-mm TST and only 4% had negative Quantiferon results. With pulmonary M. avium-intracellulare, 60% had greater than 10-mm TST and only 7% had positive Quantiferon results. The Quantiferon's mean sensitivity was 86% and specificity 94%. Although the Quantiferon does cross-react with a few NTM species, it does distinguish between TB and M. avium-intracellulare, which is the most common NTM.

The Quantiferon is currently marketed only for adults, and I don't think we have the data to support its use in children just yet. But ongoing studies should produce pediatric data in the next few years. Hopefully, this targeted test will become the new generation TB skin test substitute.