Demographic, clinical and laboratory characteristics for differential diagnosis of peripheral lymphadenopathy (LAP) and the etiologic distribution of LAP in adults; a multicenter, nested case–control study including 1401 patients from Turkey

Peripheral lymphadenopathy (LAP) is an important and common abnormal finding of the physical exam in general medical practice. We aimed to reveal the LAP etiology and demographic, clinical and laboratory variables that may be useful in the differential evaluation of LAP. This multicenter, nested case–control study including 1401 patients between 2014 and 2019 was conducted in 19 tertiary teaching and research hospitals from different regions in Turkey. The ratio of infectious, malign and autoimmune/inflammatory diseases was 31.3%, 5% and 0.3%, respectively. In 870 (62%) of patients had nonspecific etiology. Extrapulmonary tuberculosis ( n : 235, 16.8%) was the most frequent cause of LAP. The ratio of infective etiology of LAP was significantly lower in patients older than 65 years-old compared to younger patients with the rate of 66.67% and 83.84%, respectively ( p 0.016, OR 0.386, 95% Cl 0.186–0.803). The probability of malign etiology was higher both in patients who are older than 45 years-old ( p