title: Associations between cystatin C-based eGFR, ambulatory blood pressure parameters, and in-clinic versus ambulatory blood pressure agreement in older community-living adults.
abstract: OBJECTIVE
  The objective of this study was to determine the relationship between chronic kidney disease [CKD; measured using cystatin C-based estimated glomerular filtration rate (eGFR)] and abnormal ambulatory blood pressure (including nocturnal dipping) in healthy older adults. Further, this study aimed to assess the agreement between clinic and ambulatory blood pressure monitoring.
  
  
  METHODS
  Serum cystatin C levels were measured to calculate eGFR. Participants underwent clinic and 24-h ambulatory blood pressure measurements. Multiple linear regression was performed to examine the association between reduced cystatin C-based eGFR (CKDcys) and blood pressure parameters. Bland-Altman analysis was carried out to evaluate the agreement between clinic and ambulatory measurements.
  
  
  RESULTS
  The average age was 72 years. There were 60 individuals with CKDcys (eGFR<60 ml/min/1.73 m). Compared with those without CKDcys, individuals with CKDcys were older, more likely to have hypertension, and less likely to have normal dipping patterns. On multivariate analysis, the presence of CKDcys was found to be significantly associated with a lower mean ambulatory diastolic blood pressure (-2 mmHg, P=0.048), but not with nocturnal dipping or other blood pressure parameters. Clinic systolic blood pressure (SBP) significantly overestimated the mean wake-time ambulatory SBP; the mean difference was 11 mmHg for those without CKDcys (95% limits of agreement -14 to 35 mmHg) and 14 mmHg for those with CKDcys (95% limits of agreement -13 to 41 mmHg); there was no statistically significant effect modification by CKD status.
  
  
  CONCLUSIONS
  In older, seemingly healthy adults, mild CKD was associated with lower ambulatory diastolic blood pressure. The presence of CKD did not affect interpretation of clinic versus ambulatory blood pressure monitoring, although the accuracy of clinic SBP was poor.
authors.affiliation: aDepartment of Medicine, Division of Nephrology bDepartment of Family and Preventive Medicine, Division of Preventive Medicine, University of California, San Diego School of Medicine cVeterans' Affairs Healthcare System dDivision of Pulmonary and Critical Care Medicine, UC San Diego, San Diego, California eWeil-Cornell Graduate School of Medical Sciences, New York, New York, USA.
authors.forename: Tyler B
authors.initials: TB
authors.lastname: Woodell
authors.forename: Jan M
authors.initials: JM
authors.lastname: Hughes-Austin
authors.forename: Tiffany V
authors.initials: TV
authors.lastname: Tran
authors.forename: Atul
authors.initials: A
authors.lastname: Malhotra
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Abdelmalek
authors.forename: Dena E
authors.initials: DE
authors.lastname: Rifkin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000503:physiopathology*
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C