Elevated levels of whole blood nickel in a group of Sri Lankan women with endometriosis: a case control study

BACKGROUND: Endometriosis is characterized by the persistence of endometrial tissue in ectopic sites outside the uterine cavity. Presence of nickel, cadmium and lead in ectopic endometrial tissue has been reported previously. While any association between blood levels of nickel and endometriosis is yet to be described in literature, conflicting reports are available with regards to cadmium and lead levels in blood and urine. FINDINGS: In fifty patients with endometriosis and fifty age-matched controls confirmed by laparoscopy or laparotomy, whole blood samples were collected and digested using supra pure 65% HNO(3). Whole blood levels of nickel and lead were measured using Total Reflection X-ray Fluorescence (TXRF) while cadmium levels were evaluated using graphite furnace atomic absorption spectroscopy (GFASS). Women with endometriosis had significantly higher (P=0(.)016) geometric mean (95% CI) whole blood nickel levels [2.6(1.9-3.3) μg/L] as compared to women without endometriosis [0.8 (0.7-0.9) μg/L]. Whole blood levels of cadmium and lead were similar between the two groups. CONCLUSIONS: Although women with endometriosis in this study population had higher levels of nickel in whole blood compared to controls, whether nickel could be considered as an aetiological factor in endometriosis remains inconclusive in view of the smaller sample that was evaluated.