Nicotine users in Group 1 had significantly higher s-Cys than non-users (7.5+/-0.9 mg/L compared to 6.7+/-0.8; p = 0.0008), which may be a factor to include in the eGFR formulae. However, s-Cys was independent of non-renal factors such as sex, age, LBM, body weight, malnutrition and CRP and also of changes in CRP.