UCSF guidelines for creatinine testing prior to contrast administration

  1. Laboratory results should be checked for the most recent serum creatinine on ALL patients (by the technologist performing the study).
  2. If serum creatinine is not available, it should be performed IF the patient has ANY of the following risk factors:
    •    Age over 60
    •    History of “kidney disease” as an adult, including tumor and transplant
    •    Family history of kidney failure
    •    Diabetes treated with insulin or other prescribed medications
    •    Hypertension (high blood pressure)
    •    Paraproteinemia syndromes or diseases (e.g., myeloma)
    •    Collagen vascular disease (e.g., SLE, scleroderma, rheumatoid arthritis)
    •    Solid organ transplant.
  3. If creatinine testing is required, a creatinine level within the prior 6 weeks is sufficient in most clinical settings.


Background

Routine creatinine testing prior to contrast administration is NOT necessary in all patients [1, 2]. The indications for creatinine testing include those listed in the table above.  However, these recommendations should be considered in the light of several confounding factors:

  1. In a study of 2034 outpatients who all had routine creatinine testing prior to CT outpatient CT, 66 patients had a creatinine of 2.0 or above [1]. All but 2 of the 66 had one or more of 8 risk factors that were chosen based on published literature (history of renal insufficiency or renal disease, diabetes mellitus, advanced age, male gender, nephrotoxic-drug use, chemotherapy, HIV/AIDS, solitary kidney). The two cases that would have been “missed” by a policy of selective creatinine testing had a creatinine of 2.0 and 2.2. Two particularly notable findings in this study were that age alone was not an important risk factor, and that both IDDM and NIDDM were important risk factors.
  2. The use of age as a risk factor and the choice of threshold are both controversial, with conflicting data in the literature. It is also important to distinguish between studies that address age as a risk factor for an elevated baseline serum creatinine BEFORE contrast administration (which is the topic of concern when considering measuring creatinine prior to imaging) and age as a risk factor for developing contrast-induced nephropathy AFTER contrast administration. Community based studies of serum creatinine suggest age, hypertension, and diabetes are important predictors of creatinine elevation [3-5]. In addition, many centers use age (with variable thresholds) to determine the need for creatinine testing and this practice is also engrained in the department culture at UCSF.
  3. Standard practice is variable and often based on little to no evidence [6]. For example, there is little data on whether in-patients are substantively different to outpatients.
  4. Arguably, the list of risk factors should be expanded to include chemotherapy, since many of these drugs are nephrotoxic [7].
  5. Estimated glomerular filtration rate (eGFR) is likely a more reliable indicator of renal function compared to creatinine alone as it takes into account age, race and sex.  In one study, 15.2% of out-patients with a normal serum creatinine had an estimated creatinine clearance of 50 mL/min/1.73 m2 or less (normal is 90 mL/min/1.73 m2 or more) [8].  The exact eGFR threshold below which withholding intravenous contrast should be considered is unclear. The risk of contrast nephropathy rises from a low baseline in patients with an eGFR < 60 ml/min/1.732, however the majority of these patients will only have a temporary rise in creatinine. Also, there is no convincing data to support an increased morbidity or mortality in patients who do not require dialysis for the treatment of contrast nephropathy. The risk of dialysis after receiving contrast significantly increases in patients with an eGFR < 30 ml/min/1.732 [9]. The eGFR threshold below which withholding contrast should be considered is thus between 60 and 30 ml/min/1.732.  In one article [10], the rate of contrast nephropathy in patients with a GFR > 40 ml/min was 0.6% and < 40 ml/min/1.732 was 4.6%, thus a threshold of 45 ml/min/1.732 seems an appropriate cut-off.  A creatinine of 1.6 in a 70 year old, non-African American male corresponds to an estimated GFR of approximately 45 ml/min/1.732.
  6. In general, these guidelines are simply guidelines, and slavish adherence in every case is neither expected nor appropriate. Physician discretion and judgment are paramount, and commonsense should be applied to individual patient circumstances. For example, creatinine testing can be omitted for an urgent study where time is critical, particularly a contrast-enhanced stroke CT protocol requested by the Emergency Department (this determination should be made by the requesting physician). Conversely, it may be prudent to check creatinine in a sick debilitated patient even if they do not have any of the specific factors listed above.


Key Point

Routine creatinine testing prior to contrast administration is NOT necessary in all patients; the major indications are age over 70, history of preexistent renal insufficiency, diabetes mellitus, or hypertension.  Estimated glomerular filtration rate is a better predicator of renal dysfunction than creatinine alone.

References

  1. Tippins RB, Torres WE, Baumgartner BR, Baumgarten DA. Are screening serum creatinine levels necessary prior to outpatient CT examinations? Radiology 2000; 216: 481-484.
  2. Manual on Contrast Media, Edition 5.0, 2004. American College of Radiology.
  3. Culleton BF, Larson MG, Evans JC, Wilson PW, Barrett BJ, Parfrey PS, Levy D. Prevalence and correlates of elevated serum creatinine levels: the Framingham Heart Study. Arch Intern Med 1999; 159: 1785-90.
  4. Passos VM, Barreto SM, Lima-Costa MF; Bambui Health and Ageing Study (BHAS) Group. Detection of renal dysfunction based on serum creatinine levels in a Brazilian community: the Bambui Health and Ageing Study. Braz J Med Biol Res. 2003;36: 393-401.
  5. Coresh J, Wei GL, McQuillan G, Brancati FL, Levey AS, Jones C, Klag MJ. Prevalence of high blood pressure and elevated serum creatinine level in the United States: findings from the third National Health and Nutrition Examination Survey (1988-1994). Arch Intern Med. 2001; 161: 1207-16.
  6. Elicker BM, Cypel YS, Weinreb JC. IV contrast administration for CT: a survey of practices for the screening and prevention of contrast nephropathy. Am J Roentgenol 2006; 186: 1651-1658.
  7. Kintzel, PE. Anticancer Drug-Induced Kidney Disorders. Drug Safety 2001; 24:19-38.
  8. Duncan L, Heathcote J, Djurdjev O, Levin A. Screening for renal disease using serum creatinine: who are we missing? Nephrol Dial Transplant 2001; 16:1042 -1046.
  9. McCullough PA, Wolyn R, Rocher LL, Levin RN, O’Neill WW. Acute renal failure after coronary intervention: incidence, risk factors, and relationship to mortality. Am J Med 1997; 103 (5): 368-75.
  10. Thomsen HS, Morcos SK.  Risk of contrast-medium-induced nephropathy in high-risk patients undergoing MDCT – A pooled analysis of two randomized trials.  Eur Radiol 2009; 19: 891-897.