Corrected serum cystatin C-effects of thyroid dysfunctions on serum cystatin C in chronic kidney diseased patients

Abstract

Objective: To assess serum cystatin C (Cys C) and creatinine concentrations and glomerular filtration rate (GFR) in thyroid dysfunction and to determine corrected value of cystatin C in chronic kidney disease (CKD) patients with thyroid dysfunction.

Study design: Cross sectional study.

Place & study duration: Department of Chemical Pathology & Endocrinology, Armed Forces Institute of Pathology, July 2015 to January 2016.

Patients and Methods: Seventy five patients; both male and female patients of CKD with 24 hours creatinine clearance less than 60 ml/min were included. Their serum samples were analyzed for serum TSH, serum T4, serum T3 on Advia XP by chemiluminence methods and serum cystatin C on Nephstar by Nephelometry. eGFR is calculated by Modified MDRD’s equation and eGFR EPI equation by serum creatinine which was analyzed on Advia 1800® by Siemens.

Result: Out of 75 subjects, 42 (56%) were male and 33 (44%) were female. Median aged was 42.7 years (IQR: 37 years). For other quantitative variables mean±SD along with independent t- statistics were, serum cystatin C (1.27  ± 1.02 )mg/L, Serum TSH (2.95± 8.6) mIU/L Serum FT4 (13.4±3.6) pmol/L, Serum T3 (1.7±0.4) nmol/L, 24hours Creatinine Clearance (43.6± 14.9)ml/min, MDRD eGFR (59.9 ± 24.9)ml/min and CKD-EPI eGFR (61.3± 25.0)ml/min. Cystatin C had negative correlation with serum TSH (r= -0.037,p=0.750), positive correlation with T4 (R= 0.045 ,p=0.701) and T3 (r= 0.064 ,p=.585) .Cystatin C had negative correlation with GFR CrCL (r= -0.074,p=0.526), GFR MDRD (r=-0.932,p<0.05), eGFR EPI( r=-0.100,p<0.392) while GFR CrCl had significant correlation with both GFR MDRD and eGFR EPI with correlation coefficient 0.425 and 0.434 (p<0.000).

Conclusion: Corrected cystatin C calculated by adding factor of 0.04 in measured cystatin C in patients of CKD with hypothyroidism and subtracting this factor from measured cystatin C in CKD patients with hyperthyroidism improves diagnostic yield.

Key Words: Cystatin C, CKD (chronic kidney disease), Thyroid dysfunctions.