Prevalence of antinuclear antibodies in healthy Lebanese subjects, 2008-2015: a cross-sectional study involving 10,814 subjects.

Antinuclear antibodies (ANA) are found at varying frequencies in healthy populations, depending on geographical location and ethnic background of participants. The main objective of this study was to determine the prevalence of ANA in healthy Lebanese population in the period 2008-2015. Study subjects comprised 10,851 individuals (3311 males and 7503 females). ANA positivity was determined using immunofluorescence on HEp-2 cells. The prevalence of positive ANA test at a titer of ≥1:100 was 26.4 %, with 696 individuals (6.4 %) having titers exceeding 1:100. Most ANA-positive cases were recorded between 2013 and 2015, which reflected increased assay sensitivity. ANA positivity was associated with increased age and with female gender. Significant increases in ANA positivity were seen with advanced age, with steady increases from the 30- to 40-year age group through the >70-year age group, with significantly higher prevalence noted in female participants. There was a steady and significant reduction in the number of ANA-positive cases with higher ANA titers, which ranged from 20.0 % (1/100) to 3.7 % (1/320), 1.7 % (1/640), and 1.1 % (1/1000). While 45 % of low ANA titer was seen in 31-60-year age category, compared with 19.8 % for 61+ year category, the distribution of high ANA titer was more uniform between 31+ year age categories, which ranged from 11.4 % (31-40 years) to 12.4 % (>70 years). This was consistently and significantly higher in female participants. The prevalence and distribution of ANA among Lebanese individuals were comparable to the rates established for Western countries and confirm the contribution of female gender and advanced age to ANA positivity.