Heparin concentration

Polybrene concentration

Mean clotting time with cephalin 1/200

Mean clotting time with cephalin 1/10 000

Lupus Ratio


0.0 U/ml

0.00 μg/ml

29.8 seconds

46.3 seconds



0.0 U/ml

3.96 μg/ml

30.4 seconds

48.8 seconds

1.03 (neg.)

0.5 U/ml

3.96 μg/ml

29.8 seconds

46.9 seconds

1.01 (neg.)

0.5 U/ml

0.00 μg/ml

38.1 seconds

75.4 seconds

1.27 (false pos.)

 Russel Viper Venom Times were measured with two different reagents, with crude cephalin diluted 1/200 or 1/3200, respectively. Addition of unfractionated heparin to plasma without polybrene gave false positive Lupus Ratios, while addition of heparin to plasma with polybrene gave correct result. RVVTbased Lupus Ratio ≤ 1.10 = negative.