From the Guidelines
Yes, creatinine levels can be falsely elevated due to several factors, including certain medications, high-protein meals, strenuous exercise, and laboratory errors, as noted in studies such as 1 and 1.
Factors Affecting Creatinine Levels
- Certain medications like cimetidine, trimethoprim, and some cephalosporin antibiotics can interfere with creatinine secretion or measurement, as indicated in 1.
- A high-protein meal consumed before testing can temporarily raise levels, as can strenuous exercise within 24 hours of the test.
- Medical conditions such as diabetic ketoacidosis or other states causing elevated ketones may interfere with some laboratory methods.
- Substances like ascorbic acid (vitamin C) and acetone can affect certain creatinine assays.
- Laboratory errors or variations in testing methods between facilities can also contribute to falsely elevated results.
Importance of Accurate Measurement
To ensure accurate measurement, patients should inform their healthcare provider about all medications they're taking, avoid high-protein meals and strenuous exercise before testing, and consider repeating abnormal results, especially if they don't align with clinical symptoms or previous values, as suggested in 1.
Clinical Considerations
This is important because creatinine is a key marker for kidney function, and false elevations could lead to unnecessary concern or treatment, highlighting the need for careful interpretation of serum creatinine levels in the context of individual patient factors, such as muscle mass and baseline values, as discussed in 1 and 1.
From the FDA Drug Label
The presence of sulfamethoxazole and trimethoprim may also interfere with the Jaffé alkaline picrate reaction assay for creatinine, resulting in overestimations of about 10% in the range of normal values.
Yes, creatinine levels can come back falsely elevated due to interference with the Jaffé alkaline picrate reaction assay when sulfamethoxazole and trimethoprim are present, resulting in overestimations of about 10% in the range of normal values 2.
From the Research
Falsely Elevated Creatinine Levels
- Creatinine levels can come back falsely elevated due to various factors, including the presence of paraproteins, immunoglobulin M (IgM) paraproteins, and certain medications or substances 3, 4.
- Paraproteins can interfere with laboratory measurements, producing erroneous results, and an elevated creatinine with no other signs of kidney disease should prompt the idea of a spurious creatinine 3.
- IgM paraproteins can cause falsely elevated plasma creatinine values, especially when measured by enzymatic methods, and removal of high-molecular-weight proteins or addition of the patient's immunoglobulin fraction to plasma from other patients can demonstrate this interference 4.
- Other substances, such as sarcosine, can also interfere with creatinine testing assays, leading to falsely high creatinine levels, and increased sarcosine levels can be found in patients with sarcosinemia, an inborn error of amino acid metabolism 5.
- Certain medications, like trimethoprim/sulfamethoxazole, can cause pseudo-elevation of serum creatinine, which should be distinguished from true nephrotoxicity by comparing creatinine-estimated and cystatin C-estimated glomerular filtration rates 6.
- Other substances, such as 5-fluorocytosine, can also cause falsely elevated serum creatinine levels, especially when measured by enzymatic methods, and significant interference can be seen with therapeutic levels of these substances 7.