Editing C-reactive protein (section)

== Serum levels ==

{{Infobox diagnostic
| name            = C-reactive protein
| image           =
| alt             =
| caption         =
| pronounce       =
| purpose         =Detection of [[inflammation]] in body.<ref name="Lab Tests Online">{{cite web | title=C-Reactive Protein (CRP) | website=Lab Tests Online | url=https://labtestsonline.org/tests/c-reactive-protein-crp | access-date=2019-12-23}}</ref>
| test of         = The amount of CRP in the blood.<ref name="Lab Tests Online"/>
| based on        =
| synonyms        =
| reference_range =
| calculator      =
| DiseasesDB      = <!--{{DiseasesDB2|numeric_id}}-->
| ICD10           = <!--{{ICD10|Group|Major|minor|LinkGroup|LinkMajor}} or {{ICD10PCS|code|char1/char2/char3/char4}}-->
| ICD9            =
| ICDO            =
| MedlinePlus     = <!--article_number-->
| eMedicine       = <!--article_number-->
| MeshID          =
| OPS301          = <!--{{OPS301|code}}-->
| LOINC           = <!--{{LOINC|code}}-->
}}

===Measurement methods===
Traditional CRP measurement only detected CRP in the range of 10&nbsp;to&nbsp;1,000&nbsp;mg/L, whereas high sensitivity CRP (hs-CRP) detects CRP in the range of 0.5&nbsp;to&nbsp;10&nbsp;mg/L.<ref name="USPharmacist">{{cite web | vauthors = Knight ML | title = The Application of High-Sensitivity C-Reactive Protein in Clinical Practice: A 2015 Update | work = Cardiovascular | publisher = [[U.S. Pharmacist]] | date = February 18, 2015 | url = https://www.uspharmacist.com/article/the-application-of-high-sensitivity-creactive-protein-in-clinical-practice#:~:text=Defining%20hs-CRP,of%20CRP%20in%20the%20blood  | access-date = 2020-12-28 }}</ref> hs-CRP can detect [[cardiovascular disease]] risk when in excess of 3&nbsp;mg/L, whereas below 1&nbsp;mg/L would be low risk.<ref name="pmid12551878">{{cite journal | vauthors = Pearson TA, Mensah GA, Alexander RW, Anderson JL, Cannon RO, Criqui M, Fadl YY, Fortmann SP, Hong Y, Myers GL, Rifai N, Smith SC, Taubert K, Tracy RP, Vinicor F | title = Markers of inflammation and cardiovascular disease: application to clinical and public health practice: A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association | journal = Circulation | volume = 107 | issue = 3 | pages = 499–511 | date = January 2003 | pmid = 12551878 | doi = 10.1161/01.cir.0000052939.59093.45 | doi-access = free }}</ref> Traditional CRP measurement is faster and less costly than hs-CRP, and can be adequate for some applications, such as monitoring [[hemodialysis]] patients.<ref name="pmid22569431">{{cite journal | vauthors = Helal I, Zerelli L, Krid M, ElYounsi F, Ben Maiz H, Zouari B, Adelmoula J, Kheder A | title = Comparison of C-reactive protein and high-sensitivity C-reactive protein levels in patients on hemodialysis | journal = Saudi Journal of Kidney Diseases and Transplantation | volume = 23 | issue = 3 | pages = 477–483 | date = May 2012 | pmid = 22569431 | url = https://www.sjkdt.org/temp/SaudiJKidneyDisTranspl233477-6599427_181954.pdf | access-date = 2020-12-28 | url-status = dead | archive-url = https://web.archive.org/web/20211209104151/https://www.sjkdt.org/temp/SaudiJKidneyDisTranspl233477-6599427_181954.pdf | archive-date = 2021-12-09 }}</ref> Current immunoassay methods for CRP have similar precision to hsCRP performed by nephelometry and could probably replace hsCRP for cardiovascular risk assessment,<ref>{{cite journal | vauthors = Han E, Fritzer-Szekeres M, Szekeres T, Gehrig T, Gyöngyösi M, Bergler-Klein J | title = Comparison of High-Sensitivity C-Reactive Protein vs C-reactive Protein for Cardiovascular Risk Prediction in Chronic Cardiac Disease | journal = The Journal of Applied Laboratory Medicine | volume = 7 | issue = 6 | pages = 1259–1271 | date = October 2022 | pmid = 36136302 | doi = 10.1093/jalm/jfac069 }}</ref> however, in the United States this would represent off-label use, making it a laboratory-developed test under FDA regulations.<ref>{{cite journal | vauthors = Wolska A, Remaley AT | title = CRP and High-Sensitivity CRP: "What's in a Name?" | journal = The Journal of Applied Laboratory Medicine | volume = 7 | issue = 6 | pages = 1255–1258 | date = October 2022 | pmid = 36136105 | doi = 10.1093/jalm/jfac076 | doi-access = free }}</ref>

===Normal===
In healthy adults, the normal concentrations of CRP varies between 0.8&nbsp;mg/L and 3.0&nbsp;mg/L. However, some healthy adults show elevated CRP at 10&nbsp;mg/L. CRP concentrations also increase with age, possibly due to [[subclinical]] conditions. There are also no [[seasonal variation]]s of CRP concentrations. [[Gene polymorphism]] of [[interleukin-1 family]], [[interleukin 6]], and polymorphic GT repeat of the CRP gene do affect the usual CRP concentrations when a person does not have any medical illnesses.<ref name=Pepys/>

===Acute inflammation===
When there is a stimulus, the CRP level can increase 10,000-fold from less than 50&nbsp;μg/L to more than 500&nbsp;mg/L. Its concentration can increase to 5&nbsp;mg/L by 6 hours and peak at 48 hours. The plasma half-life of CRP is 19 hours, and is constant in all medical conditions.<ref>{{cite journal | vauthors = Vigushin DM, Pepys MB, Hawkins PN | title = Metabolic and scintigraphic studies of radioiodinated human C-reactive protein in health and disease | journal = The Journal of Clinical Investigation | volume = 91 | issue = 4 | pages = 1351–1357 | date = April 1993 | pmid = 8473487 | pmc = 288106 | doi = 10.1172/JCI116336 }}</ref> Therefore, the only factor that affects the blood CRP concentration is its production rate, which increases with inflammation, infection, trauma, necrosis, malignancy, and [[allergic reaction]]s.{{citation needed|date=August 2023}} Other inflammatory mediators that can increase CRP are [[TGF beta 1]], and [[tumor necrosis factor alpha]]. In acute inflammation, CRP can increase as much as 50 to 100&nbsp;mg/L within 4 to 6 hours in mild to moderate inflammation or an insult such as [[skin infection]], [[cystitis]], or [[bronchitis]]{{clarify|date=August 2022}}. It can double every 8 hours and reaches its peak at 36 to 50 hours following injury or inflammation. CRP between 100 and 500&nbsp;mg/L is considered highly predictive of inflammation due to bacterial infection.  Once inflammation subsides, CRP level falls quickly because of its relatively short half-life.<ref name="Bray 2016"/>

===Metabolic inflammation===
CRP concentrations between 2 and 10&nbsp;mg/L are considered as metabolic inflammation: metabolic pathways that cause [[arteriosclerosis]]<ref>{{cite journal | vauthors = Nilsson J | title = CRP--marker or maker of cardiovascular disease? | journal = Arteriosclerosis, Thrombosis, and Vascular Biology | volume = 25 | issue = 8 | pages = 1527–1528 | date = August 2005 | pmid = 16055753 | doi = 10.1161/01.ATV.0000174796.81443.3f | doi-access = free }}</ref> and [[type II diabetes mellitus]].<ref>{{cite journal | vauthors = Wang X, Bao W, Liu J, Ouyang YY, Wang D, Rong S, Xiao X, Shan ZL, Zhang Y, Yao P, Liu LG | title = Inflammatory markers and risk of type 2 diabetes: a systematic review and meta-analysis | journal = Diabetes Care | volume = 36 | issue = 1 | pages = 166–175 | date = January 2013 | pmid = 23264288 | pmc = 3526249 | doi = 10.2337/dc12-0702 }}</ref>