Editing Creatinine (section)

=== Serum creatinine ===
Diagnostic serum creatinine studies are used to determine renal function.<ref name="Lewis_2016" /> The reference interval is 0.6–1.3&nbsp;mg/dL (53–115 μmol/L).<ref name="Lewis_2016" /> It is simple to measure serum creatinine, and it is the most commonly used indicator of renal function.<ref name=ClinChem89>{{cite book| vauthors = Taylor EH |title=Clinical Chemistry|year=1989|publisher=Wiley |isbn=0-471-85342-9 |oclc=19065010 |pages=4, 58–62}}</ref>

A rise in blood creatinine concentration is a late marker, observed only with marked damage to functioning [[nephron]]s. The test is therefore unsuitable for detecting early-stage [[kidney disease]]. A better estimate of kidney function is given by calculating the estimated glomerular filtration rate (eGFR). eGFR can be calculated without a 24-hour urine collection, using serum creatinine concentration and some or all of the following variables: sex, age, and weight, as suggested by the [[American Diabetes Association]].<ref>{{cite journal | vauthors = Gross JL, de Azevedo MJ, Silveiro SP, Canani LH, Caramori ML, Zelmanovitz T | title = Diabetic nephropathy: diagnosis, prevention, and treatment | journal = Diabetes Care | volume = 28 | issue = 1 | pages = 164–76 | date = January 2005 | pmid = 15616252 | doi = 10.2337/diacare.28.1.164 | doi-access = free }}</ref> Many laboratories will automatically calculate eGFR when a creatinine test is requested. Algorithms to estimate GFR from creatinine concentration and other parameters are discussed in the [[Renal function#Estimated values|renal function]] article. Unfortunately, the MDRD Study equation was developed in people with chronic kidney disease, and its major limitations are imprecision and systematic underestimation of measured GFR (bias) at higher/normal values.<ref>{{cite journal | vauthors = Levey AS, Stevens LA, Schmid CH, Zhang YL, ((Castro AF 3rd)), Feldman HI, Kusek JW, Eggers P, Van Lente F, Greene T, Coresh J| title = A new equation to estimate glomerular filtration rate | journal = Ann Intern Med | date = 5 May 2009 | volume = 150 | issue = 9 | pages = 604–612 | pmid = 19414839 | pmc = 2763564 | doi = 10.7326/0003-4819-150-9-200905050-00006 | doi-access = free }}</ref>  

A concern as of late 2010 relates to the adoption of a new analytical method, and the possible effect this may have in clinical medicine.  Most clinical laboratories now align their creatinine measurements against a new standardized [[isotope dilution mass spectrometry]] (IDMS) method to measure serum creatinine. IDMS appears to give lower values than older methods when the serum creatinine values are relatively low, for example 0.7&nbsp;mg/dL. The IDMS method would result in comparative overestimation of the corresponding calculated GFR in some patients with normal renal function. A few medicines are dosed even in normal renal function using that derived value of GFR. The dose, unless further modified, could then be higher than desired, potentially causing increased drug-related toxicity. To counter the effect of changing to IDMS, new FDA guidelines have suggested limiting doses of carboplatin, a chemotherapy drug, to specified maxima.<ref>{{cite web|url=https://www.fda.gov/AboutFDA/CentersOffices/CDER/ucm228974.htm|archive-url=https://web.archive.org/web/20111119090611/https://www.fda.gov/AboutFDA/CentersOffices/CDER/ucm228974.htm|archive-date=2011-11-19|title=Carboplatin dosing|website=[[Food and Drug Administration]]|department=Center for Drug Evaluation and Research|url-status=dead}}</ref>

A 2009 Japanese study found a lower serum creatinine concentration to be associated with an increased risk for the development of type 2 diabetes in Japanese men.<ref>{{cite journal | vauthors = Harita N, Hayashi T, Sato KK, Nakamura Y, Yoneda T, Endo G, Kambe H | title = Lower serum creatinine is a new risk factor of type 2 diabetes: the Kansai healthcare study | journal = Diabetes Care | volume = 32 | issue = 3 | pages = 424–6 | date = March 2009 | pmid = 19074997 | pmc = 2646021 | doi = 10.2337/dc08-1265 }}</ref>