Cardiac troponin is the preferred biomarker for the diagnosis of acute myocardial infarction. Whereas the diagnosis is based on an increase and/or decrease in the concentrations of cardiac troponins with at least one value above the 99th percentile value of the reference population together with the evidence of ischemia, serial sampling is needed. Knowledge of the variation in cardiac troponin levels over time in individuals in a normal rest state (not during an acute myocardial infarction), also called the biological variation, is important regarding the interpretation of the serial cardiac troponin levels. A recent study by our group showed a circadian rhythm in cardiac troponin levels. This circadian rhythm is important regarding the interpretation of the serial cardiac troponin levels.

Increased cTnI and cTnT concentrations are common in subjects with renal impairment. The mechanism of the elevated concentration of cTn in these subjects is still unclear. It is hypothesized that impaired renal clearance contributes to elevated levels of cTn. However, it is not clear whether renal function affects the biological variation and circadian rhythm of cTn. The monitoring of the biological variation and circadian rhythm of cTn in subjects with impaired renal function creates the opportunity to assess the effect of renal clearance on the circadian rhythm of cardiac troponins.

Inclusion Criteria:

• CKD stage 3 or 4
• No dialysis
• No evidence of active, acute cardiovascular disease

Exclusion Criteria:

• History of acute myocardial infarction in the last year
• History of pulmonary embolism in the last six months
• Anemia (Hb < 6.5 mmol/L)

Individuals with chronic kidney disease (CKD) stage 3 and 4