The effect of fish oil on two-step tuberculin test in hospitalized patients: A randomized controlled trial

According to national tuberculosis control guide, two-step tuberculin skin test (TST) should be done in the elderly, if the initial test is negative. However, it raises questions about the usefulness of this approach.
This study aimed to explore the effects of fish oil supplements on the two-step tuberculin test in hospitalized patients.
In this randomized controlled clinical trial, 128 patients randomly allocated to control group (receiving placebo, n=64) and treatment group (receiving fish oil supplements, n=64) during 2016. Fish oil supplement group was treated with 2 g daily for 4 consecutive days. The outcome was considered a change in 2 sequential TST induration sizes. Significant increase in the size of the secondary induration compared to primary was considered 6 mm or more.
Findings: There was significant difference between primary and secondary indurations of two groups (higher in treatment group) (P=0.04). According to the results of analysis of variance and correlation tests, two effective factors were identified: initial induration and residence location (P=0.014 and P=0.002, respectively). In both groups, no clinically significant increase in the size of induration was observed.
It seems that the number of cases considered as infected with tuberculosis does not increase with two- rather than one-step tuberculin skin test. Also, the short-term administration of fish oil supplements does not change this result.