A lupus anticoagulant neutralization procedure using the patient's own platelets
Carroll, P.; Ray, M.; Just, S.; Hawson, G.
Blood Coagulation and Fibrinolysis An International Journal in Haemostasis and Thrombosis 5(4): 523-527
1994
ISSN/ISBN: 0957-5235 PMID: 7841308 Document Number: 438040
An auto platelet neutralization procedure (APNP) which assists identification of lupus anticoagulants (LA) is described. Patient platelet-rich plasma is frozen then thawed (PRPF) and an activated partial thromboplastin time (aPTT) is performed on both platelet-poor plasma and PRPF. The degree of correction between the two plasmas is calculated and the percentage APNP is obtained. A lupus anticoagulant was suspected if a sample had a prolonged aPTT and at least two out of three of the following characteristics: (1) aPTT resistant to correction with equal parts normal plasma, (2) prolonged kaolin clotting time mixing test (DELTA-KCT), (3) prolonged dilute Russell's Viper Venom Time that did not correct with normal plasma (DRVVR). Ten normal volunteers had mean (+- SD) APNP of 7.7 +- 4.3%. Fifty LA negative patients with normal aPTT, DELTA-KCT and DRVVR, had a mean APNP of 10.0 +- 6.3%. Twenty-eight patients suspected as LA positive had APNP gt 25% with a mean of 39.0 +- 7.5%. Twenty-one patients with prolonged aPTT attributed to factor deficiency had APNP lt 25% with a mean of 6.3 +- 12.0%. LA was also suspected in two other patients with prolonged aPTT that did not meet the above criterion but had APNP gt 25%. In three patients with normal aPTT, LA was suspected and APNP ranged from 21 to 28%. An intermediate APNP range of 20-25% may be suggestive of LA in patients with normal aPTT. The APNP did not appear to be affected by platelet count in the samples tested unless the platelet count in PRP was less than 175 times 10-4/l. The APNP appears to be an effective discriminator between factor deficiency and LA. Any laboratory with the ability to perform an aPTT can perform the technique and no additional reagents are required.