Serum adenosine deaminase and tuberculin skin test in children with tuberculosis contact

Background: The tuberculin skin test (TST) is used in children who have been in contact with tuberculosis (TB). The test has limitations in terms of operator variability and the need for a second visit at 48–72 h for interpretation. Serum adenosine deaminase (ADA) was studied in adults and found to have a strong correlation with TST. Until now no data are available in the pediatric population. Objective: To examine the correlation between serum ADA and the TST in children who had been in contact with TB. Materials and Methods: A prospective study was conducted at Songklanagarind Hospital in southern Thailand among children aged 2–15 years with a history of contact TB between 2016 and 2018. Serum ADA was obtained before performing the TST. Children with active TB disease were excluded from the analysis. Results: Sixty-seven children were enrolled. The serum ADA ranged from 9.3–43 IU/L. The overall correlation between serum ADA and TST was poor (ρ = −0.03, P = 0.84). However, a subgroup analysis excluding 32 children with TST size 0 mm and a high variation of serum ADA (10–37.6 IU/L) found that in the remaining children, serum ADA and TST had a moderate correlation with statistical significance (ρ = 0.48, P = 0.004). Conclusions: The correlation between serum ADA and TST in contact TB pediatric patients was poor. The cause of low correlation was due to a high variability of serum ADA level in children who had no reaction to TST.