Determination of Rennet Clotting Time by Texture Analysis Method

In this study, texture analysis method was used for the determination of rennet flocculation time (tfloc) and rennet clotting time (tclot) of rennet-induced reconstitued milk samples with different CaCl2 concentrations. The rennet flocculation time (RFT) and rennet clotting time (RCT) were also determined by using the Berridge test and sensory evaluation. The hardness value versus renneting time curves derived from texture analysis gave a good modified exponential relationship for each CaCl2 concentration and the curves were used to calculate flocculation time and clotting time parameters. It was found that the parameters (tfloc and tclot) appeared strongly correlated with RFT and RCT, respectively. Texture analysis was proved as a suitable method to control the rennet-induced coagulation and determine the rennet clotting time. It was also determined that enrichment of milk with CaCl2 leaded to a decrease in flocculation and clotting times and an increase in rate of clotting and gel hardness.

Effects of low molecular weight heparin on clot rate and activated clotting time： an in vitro study

Background Due to lack of point-of-care testing, the use of low-molecular-weight heparin （LMWH） therapy in some special patients is restricted. This study was designed to explore the effects of LMWH on clot rate （CR） and activated clotting time （ACT）, and to search for an appropriate method for bedside monitoring of anticoagulant activity of LMWH. Methods Thirty-two healthy volunteers were selected from the staff of Beijing Tongren Hospital. CR and ACT were measured with different reagents （glass beads, diatomite, kaolin and magnetic bar） on blood samples spiked with increasing concentrations of LMWH （dalteparin, 0.2-1.8 IU/ml）. Correlations between concentrations of LMWH and values of CR and ACT were analysed based on the data obtained and regression analysis was performed to establish a regression equation. Results With the increase in doses of dalteparin, CR values reduced gradually. The values of CR of four reagents （glass beads, diatomite, kaolin and magnetic bar） were 20.4-4.5 IU/min, 27.4-6.9 IU/min, 27.5-7.9 IU/min and 7.8-0.1 IU/min respectively and an linear relationship was observed between the CR values and dalteparin concentrations （P〈0.05）. The values of ACT were 173-615 seconds, 130-270 seconds, 123-226 seconds, 337-1411 seconds respectively, which showed a linear regression between the ACT values and dalteparin concentrations （P〈0.01）. Differences in slope of the regression curves of ACT were observed with all the reagents tested （glass beads 248.2 s/IU, diatomite 74.8 s/IU, kaolin 58.2 s/IU and magnetic bar 1112.2 s/IU, P〈0.01）. While the minimum concentration of dalteparin was 0.2 IU/ml, 0.4 IU/ml, 1.4 IU/ml and 0.2 IU/ml separately, the ACT values of the four coagulants （glass beads, diatomite, kaolin and magnetic bar） were beyond the normal limit and showed a noticeable increase respectively （P〈0.01）. Conclusions This study showed that there was an excellent linear relationship between the CR and ACT values and dalteparin concentrations for all the four reagents （glass beads, diatomite, kaolin and magnetic bar） in vitro. The sensitivity of different coagulation reagents to LMWH different. Choosing a suitable reagent, both CR and ACT were possible to be used as a convenient bedside test for LMWH.

In vitro anticoagulation monitoring of low-molecular-weight heparin

Background Although low-molecular-weight heparin has replaced unfractionated heparin to become the primary anticoagulation drug for treatment of acute coronary syndrome, there is no convenient bedside monitoring method. We explored the best laboratory monitoring method of low-molecular-weight heparins （enoxaparin, dalteparin, and nadroparin） by use of the Sonoclot coagulation analyzer to monitor the activated clotting time. Methods A total of 20 healthy volunteers were selected and 15 ml of fasting venous blood samples were collected and incubated. Four coagulants, kaolin, diatomite, glass bead, and magnetic stick, were used to determine the activated clotting time of the low-molecular-weight heparins at different in vitro anti-Xa factor concentrations. A correlation analysis was made to obtain the regression equation. The activated clotting time of the different low-molecular-weight heparins with the same anti-Xa factor concentration was monitored when the coagulant glass beads were applied. Results The activated clotting time measured using the glass beads, diatomite, kaolin, and magnetic stick showed a linear correlation with the concentration of nadroparin （r = 0.964, 0.966, 0.970, and 0.947, respectively）. The regression equation showed that the linear slopes of different coagulants were significantly different （glass beads 230.03 s/IU, diatomite 89.91 s/IU, kaolin 50.87 s/IU, magnetic stick could not be calculated）. When the concentration of the anti-Xa factor was the same for different low-molecular-weight heparins, the measured activated clotting time was different after the application of the glass bead coagulant. Conclusions The glass bead coagulant is most feasible for monitoring the in vitro anticoagulation activity of nadroparin The different effects of different low-molecular-weight heparins on the activated clotting time may be related to the different anti-11a activities.