A lupus anticoagulant neutralization procedure using the patient's own platelets.

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 > 25% with a mean of 39.0 +/- 7.5%. Twenty-one patients with prolonged aPTT attributed to factor deficiency had APNP < 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 > 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 effected by platelet count in the samples tested unless the platelet count in PRP was less than 175 x 10(9)/1.(ABSTRACT TRUNCATED AT 250 WORDS)