Table 2.

Anti-Xa activity in plasma and breast milk.

Patient number	IU ml−1 plasma*	IU ml−1 breast milk*	Milk/plasma ratio
01	0.191	0.017	0.089
02‡	0.308	0.006	0.02
03	0.201	0.012	0.06
04	0.087	0.017	0.195
05	0.260	0.027	0.104
06	0.264	0.012	0.046
07	0.192	<0.005+	<0.026
08	0.198	<0.005+	<0.025
09	0.103	0.017	0.165
10	0.180	<0.005+	<0.028
11	0.165	0.037	0.224
12	0.254	0.021	0.083
13	0.175	0.028	0.16
14	0.074	<0.005+	<0.068
15	0.163	0.007	0.043

^*Anti-Xa activity determined using a clotting time assay developed and performed by P. Lang, Quality Control & Assurance, F. Hoffmann-La Roche, Basel, Switzerland.

⁺+Limit of quantification was set at the lowest point on the standard calibration curve plotted for each sample (t = 0).

^‡The recovery rate for a 0.045 IU ml⁻¹ spike of low molecular weight heparin added to the plasma of this patient (t = 0) was 88.9%.