{{Hatnote|Not to be confused with ''Kaolin cephalin clotting time''.}} {{Infobox diagnostic | name = Kaolin clotting time | image = | caption = | test of = Blood plasma<ref>{{cite book |last1=Gronowski |first1=Ann M. |title=Handbook of Clinical Laboratory Testing During Pregnancy |date=2004 |publisher=Springer Science & Business Media |isbn=9781592597871 |page=308 |url=https://books.google.com/books?id=Dt_OBgAAQBAJ&pg=PA308 |language=en}}</ref> }}
'''Kaolin clotting time''' ('''KCT''') is a sensitive test to detect lupus anticoagulants.<ref name="Radhakrishnan">{{cite book | doi = 10.1007/978-1-62703-339-8_25 | pmid=23546725 | chapter=Kaolin Clotting Time | series=Methods in Molecular Biology | volume=992 | date=2013 | pages=335–339 | first=Kottayam | last=Radhakrishnan| title=Haemostasis | isbn=978-1-62703-338-1 }}</ref> There is evidence that suggests it is the most sensitive test for detecting lupus anticoagulants.<ref name="Exner">{{Cite journal | pmid = 2128977| year = 1990| last1 = Exner| first1 = T| title = Comparison of test methods for the lupus anticoagulant: International survey on lupus anticoagulants-I (ISLA-1)| journal = Thrombosis and Haemostasis| volume = 64| issue = 3| pages = 478–84| last2 = Triplett| first2 = D. A.| last3 = Taberner| first3 = D. A.| last4 = Howard| first4 = M. A.| last5 = Harris| first5 = E. N.| doi=10.1055/s-0038-1647340| s2cid = 32243774}}</ref> It can also detect factor VIII inhibitors but is sensitive to unfractionated heparin as well.<ref name="practical-haemostasis.com">{{cite web |url=http://www.practical-haemostasis.com/Thrombophilia%20Tests/APS/kct.html/ |title=Kaolin Clotting Time [KCT] |accessdate=26 November 2014 |archive-url=https://web.archive.org/web/20141126134615/http://www.practical-haemostasis.com/Thrombophilia%20Tests/APS/kct.html |archive-date=26 November 2014 |url-status=dead }}</ref>
The KCT on whole blood is known as the "Activated Clotting Time" (ACT) and is widely used in various instruments during surgery such as cardiac bypass to monitor heparin.<ref>De Vries, A.J.; Lansink-Hartgring, A, O.; Fernhout, F.J.; Huet, R, C, G.; van den Heuvel, E, R. (2017) "The activated clotting time in cardiac surgery: should celite or kaolin be used?" Interact Cardiovascular and Thoracic Surgery. 24 (4): 549-554</ref>
==History== KCT was first described by Dr. Joel Margolis in 1958.<ref name="Margolis">{{Cite journal | pmid = 13575555| pmc = 479806| year = 1958| last1 = Margolis| first1 = J| title = The kaolin clotting time; a rapid one-stage method for diagnosis of coagulation defects| journal = Journal of Clinical Pathology| volume = 11| issue = 5| pages = 406–9| doi=10.1136/jcp.11.5.406}}</ref> Later on, it was found to be very sensitive to lupus anticoagulants but was only reliable when test plasmas were mixed with normal plasma in various proportions.<ref name="Exner" /> It became the preferred method for lupus anticoagulant testing after Dr. Wilhelm Lubbe showed it to be a good marker for recurrent fetal loss.<ref>Lubbe, W.F.; Butler, W.S.; Palmer, S.J.; Liggins, G.C. (1983). "Fetal survival after prednisone suppression of maternal lupus-anticoagulant". Lancet. June 18;(8338):1361-3</ref>
==Principle== KCT is similar to the activated partial thromboplastin time test, except it does not use exogenous phospholipid.<ref name="Radhakrishnan"/> Thus, a confirmatory test that uses excess phospholipid is needed to validate the presence of lupus anticoagulants.<ref name="Radhakrishnan"/> Otherwise, diluting the test plasma in normal plasma before testing provides characteristic mixing patterns.<ref name="Exner2">Exner, T (1978). "A sensitive test demonstrating lupus anticoagulant and its behavioural patterns". British Journal of Haematology. 40 (1): 143-51.</ref>
Kaolin is the surface activator, and the test also requires small amounts of cell fragments and plasma lipids to provide the phospholipid surface required for coagulation.<ref name="Radhakrishnan"/><ref name="practical-haemostasis.com"/> Therefore, the sample quality is important for the validity of the screening test.<ref name="Radhakrishnan"/>
==Method== thumb|200px|right|Kaolin The test combines a test plasma with kaolin, and after a brief pre-incubation and the addition of calcium chloride, the time to clot (in seconds) is measured.<ref name="Margolis"/> Mixes of patient plasma with normal plasma are recommended for testing.<ref name="Kraemer">Ledford-Kraemer, L. et al (2014). "Laboratory testing for the lupus anticoagulant". CLSI; H60 1st edition.</ref>
==Interpretation== The KCT test/control ratio of greater than or equal to 1.2 indicates that a defect is present.<ref name="practical-haemostasis.com" /> If the test/control ratio is between 1.1 and 1.2, the test is equivocal.<ref name="practical-haemostasis.com" />
A good way of expressing the result using mixes is to calculate the Rosner index.<ref>Rosner, R.; Pauzner, R.; Lusky, A. (1987). "Detection and quantitative evaluation of lupus anticoagulant activity". Thrombosis and Haemostasis.57;144-7.</ref> If A is the KCT of normal plasma, B is that of the 1:1 mix and C is that of the patient plasma, then the Rosner index is 100x(B-A)/C. Values above 15 indicate a positive result but in most cases labs set their own cutoff values.<ref name="Kraemer" />
If the KCT is less than 60 seconds, this suggests that the test plasma is contaminated with platelet fragments; therefore, the test is not valid.<ref name="practical-haemostasis.com" />
==See also== * Dilute Russell's viper venom time * Partial thromboplastin time * Activated clotting time
==References== {{reflist}}
Category:Blood tests