Coagulation Reagents

Activated Partial Thromboplastin Time

Diagnostic reagent for the in-vitro quantitative determination of activated partial thromboplastin time (APTT) in human plasma, using ellagic acid as an activator in both automatic and manual systems.

Range	Coagulation Reagents
Type of specimen	Plasma. The blood should be collected by careful venipuncture and transferred into a tube containing trisodium citrate (0.11 mol/L, 3.2%); mix blood with the anticoagulant at a ratio of 9:1 (4.5 ml blood + 0.5 ml sodium citrate), avoiding foam formation during mixing. For occasional patients with a haematocrit below 20% or above 55%, this ratio must be readjusted to ensure a valid result. Platelet factor IV, a heparin-neutralizing factor, can be released due to platelet aggregation or damage; to prevent this in vitro, the specimen should be collected with a minimum of trauma. Pooled plasma: prepare a fresh normal plasma pool (FNP) from at least five normal healthy donors and process as above; plasma must be tested within 3 hours of blood collection.
Specimen handling	Centrifuge immediately for 15 minutes at 1500–3000 rpm (approximately 1500 g) and transfer the plasma into a clean test tube; it should be ensured that the plasma is free from platelets. Cap the test tubes to prevent deterioration of samples. Plasma must be tested immediately; if the specimens are held at 2–4 °C they may be tested within 3 hours.
Interfering substances	Heparin, depending on its origin and composition (calcium or sodium salt), has a different influence on the sensitivity of the reagent. Significant interference of bilirubin levels above 60 µmol/L. Turbidity caused negative interference above 0.2%.
Storage	LS-Thrombocelin reagent is ready to use and is stable until the expiry date on the label when properly stored refrigerated at 2–8 °C (do not freeze). Stability: 1 week at 15–25 °C, 2 days at 37 °C. The reagent is normally clear; do not use it if it is turbid or contaminated.
Catalogue numbers	5