Kaolin clotting time

Kaolin clotting time (KCT) is a sensitive test to detect lupus anticoagulants.[2] There is evidence that suggests it is the most sensitive test for detecting lupus anticoagulants.[3] It can also detect factor VIII inhibitors but is sensitive to unfractionated heparin as well.[4]

Not to be confused with Kaolin cephalin clotting time.
Kaolin clotting time
Test ofBlood plasma[1]

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.[5]

History

KCT was first described by Dr. Joel Margolis in 1958.[6] 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.[3] It became the preferred method for lupus anticoagulant testing after Dr Wilhelm Lubbe showed it to be a good marker for recurrent fetal loss.[7]

Principle

KCT is similar to the activated partial thromboplastin time test, except it does not use exogenous phospholipid.[2] Thus, a confirmatory test that uses excess phospholipid is needed to validate the presence of lupus anticoagulants.[2] Otherwise diluting the test plasma in normal plasma before testing provides characteristic mixing patterns.[8]

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.[2][4] Therefore, the sample quality is important for the validity of the screening test.[2]

Method
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.[6] Mixes of patient plasma with normal plasma are recommended for testing.[9]

Interpretation

The KCT test/control ratio of greater than or equal to 1.2 indicates that a defect is present.[4] If the test/control ratio is between 1.1 and 1.2, the test is equivocal.[4]

A good way of expressing the result using mixes is to calculate the Rosner index.[10] 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.[9]

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.[4]

See also

References
  1. Gronowski, Ann M. (2004). Handbook of Clinical Laboratory Testing During Pregnancy. Springer Science & Business Media. p. 308. ISBN 9781592597871.
  2. Radhakrishnan, Kottayam (2013). "Kaolin Clotting Time". Haemostasis. Methods in Molecular Biology. Vol. 992. pp. 335–339. doi:10.1007/978-1-62703-339-8_25. ISBN 978-1-62703-338-1. PMID 23546725.
  3. Exner, T; Triplett, D. A.; Taberner, D. A.; Howard, M. A.; Harris, E. N. (1990). "Comparison of test methods for the lupus anticoagulant: International survey on lupus anticoagulants-I (ISLA-1)". Thrombosis and Haemostasis. 64 (3): 478–84. doi:10.1055/s-0038-1647340. PMID 2128977.
  4. "Kaolin Clotting Time [KCT]". Archived from the original on 26 November 2014. Retrieved 26 November 2014.
  5. 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
  6. Margolis, J (1958). "The kaolin clotting time; a rapid one-stage method for diagnosis of coagulation defects". Journal of Clinical Pathology. 11 (5): 406–9. doi:10.1136/jcp.11.5.406. PMC 479806. PMID 13575555.
  7. 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
  8. Exner,T (1978). "A sensitive test demonstrating lupus anticoagulant and its behavioural patterns". British Journal of Haematology. 40 (1): 143-51.
  9. Ledford-Kraemer, L. et al (2014). "Laboratory testing for the lupus anticoagulant". CLSI; H60 1st edition.
  10. Rosner, R.; Pauzner, R.; Lusky, A. (1987). "Detection and quantitative evaluation of lupus anticoagulant activity". Thrombosis and Haemostasis.57;144-7.
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