Recommendations for monitoring patients on LMWH (South African Society of Thrombosis and Haemostasis 2004) (4) * The patient's platelet count should be checked on initiation of LMWH, after 5 days, and thereafter not less than once every 3 months, while on therapy * Anticoagulant activity is measured using an anti-Xa activity assay * Anti-Xa measurement is only indicated in pregnancy, renal failure or in excessively obese patients in whom large doses are required * The anti-Xa assay
must be calibrated for each LMWH tested * The anti-Xa assay
is available for enoxaparin and nadroparin at Johannnesburg Hospital Haematology Laboratory, tel (011) 488-3068 or (011) 489-8552 * 5 ml citrated blood taken 3 hours after a LMWH dose is required for the assay Target levels: Prophylaxis target: 0.
In addition, calibrators with Riva concentrations of 0, 15, 60, 100, and 150 [micro]g/L were sent to 18 Finnish laboratories for the local anti-Xa assay
The anti-Xa assay
for enoxaparin and nadroparin is currently available from the Johannesburg Hospital Haematology Laboratory (011 488-3068 or 011 489-8552), as well as from most private laboratories.
4 anti-Xa Chromogenic anti-Xa heparin heparin (LMWH) heparin U/mL assay (enoxaparin, Lovenox) Pentasaccharide Chromogenic anti-Xa assay
(fondaparinux, using plasma w/ fondaparinux Arixtra) for standard curve Table 3.
Due to the extensive number of such patients, the availability of a chromogenic anti-Xa assay
, readily and always available is key in ensuring effective monitoring, 24 hours a day/7 day a week.
Heparin was measured with an anti-Xa assay
performed on the MDA (BioMerieux).