Compared with the general Dutch population, the A-allele of the IFNG rs1861493 SNP was more often present in participants with a low symptom score and less often in participants with a high symptom score; a borderline significant result was found for participants with a higher symptom score compared with the community controls (OR: 1.55; 95 % CI: 0.96–2.50; p = 0.069).
A similar result was found for one of the IFNG SNPs (rs1861493) when using the median symptom score as the cut-off (the A-allele was less frequently observed among the participants with the above median symptom score), while the other IFNG SNP (rs2430561) showed a trend in association in the same direction (the T-allele was less frequently observed among the participants with the above median symptom score), though it was no longer statistically significant.