Measurement of prothrombin time (PT) and activated partial thromboplastin time (APTT) on canine citrated plasma samples following different storage conditions

Samples from 75 clinically ill dogs were utilised in the study. APTT and PT tests were performed immediately on fresh citrated plasma samples (Fresh). The remaining plasma was stored at -20 degrees C for less than 4 months (n=36 samples) or between 4 and 7 months (n=39 samples). In batches of five, frozen samples were thawed rapidly and APTT and PT tests were performed on the thawed samples immediately (0RT) and after storage at room temperature (23 degrees C, range: 22-25 degrees C) for 24h (24RT) and 48h (48RT). The median APTT value from the (0RT) samples was significantly longer than that obtained from fresh samples (15s vs. 13.2s) but the PT value was not statistically different (7.8s vs. 7.6s). The median APTT (15s) and PT (7.5s) results from the (24RT) samples were not statistically different to those from the (0RT) samples (APTT: 15s, PT: 7.6s) but both tests were significantly longer (APTT: 16.5s, PT: 9.2s) from the (48RT) samples. We concluded that long term batching and freezing of clinical samples at -20 degrees C is acceptable for measurement of PT but not of APTT. We demonstrated that APTT and PT results do not change following storage of samples at room temperature for 24h but storage for 48h may lead to statistically and clinically significant changes (values at least 25% higher than the high value of the laboratory's reference interval) in both clotting times.     

Comparison of prothrombin time, activated partial thromboplastin time, and fibrinogen concentration in blood samples collected via an intravenous catheter versus direct venipuncture in dogs

OBJECTIVE: To compare prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen concentration in canine blood samples collected via an indwelling IV catheter and direct venipuncture. ANIMALS: 35 dogs admitted to an intensive care unit that required placement of an IV catheter for treatment. PROCEDURES: Blood samples were collected via IV catheter and direct venipuncture at the time of catheter placement and 24 hours after catheter placement. Prothrombin time, APTT, and fibrinogen concentration were measured. RESULTS: 5 dogs were excluded from the study; results were obtained for the remaining 30 dogs. Agreement (bias) for PT was -0.327 seconds (limits of agreement, -1.350 to 0.696 seconds) and 0.003 seconds (limits of agreement, -1.120 to 1.127 seconds) for the 0- and 24-hour time points, respectively. Agreement for APTT was -0.423 seconds (limits of agreement, -3.123 to 2.276 seconds) and 0.677 seconds (limits of agreement, -3.854 to 5.207 seconds) for the 0- and 24-hour time points, respectively. Agreement for fibrinogen concentration was -2.333 mg/dL (limits of agreement, -80.639 to 75.973 mg/dL) and -1.767 mg/dL (limits of agreement, -50.056 to 46.523 mg/dL) for the 0- and 24-hour time points, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Agreement between the 2 techniques for sample collection was clinically acceptable for PT, APTT, and fibrinogen concentration at time 0 and 24 hours. It is often difficult or undesirable to perform multiple direct venipunctures in critically ill patients. Use of samples collected via an IV catheter to monitor PT and APTT can eliminate additional venous trauma and patient discomfort and reduce the volume of blood collected from these compromised patients.     

Effects of haemolysis, lipaemia and bilirubinaemia on prothrombin time, activated partial thromboplastin time and thrombin time in plasma samples from healthy dogs

Interferences caused by haemolysis, lipaemia and bilirubinaemia on prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT in normal canine plasma samples were studied using commercially available reagents and a steel ball coagulometer. Haemolysis significantly interfered with APTT (P = 0.0076) and TT (P = 0.0292). Regression analysis showed that TT was significantly shortened as haemoglobin concentrations increased. Lipaemia increased as demonstrated by regression analysis. Bilirubin significantly interfered with PT (P=0.0003) and APTT (P=0.002). Although statistically significant, none of the differences found were of clinical relevance.     

One-stage prothrombin time, activated partial thromboplastin time, thrombin time, fibrin degradation product concentration, and antithrombin activity in healthy adult alpacas

Background: Alpacas are increasingly presented to veterinarians for evaluation and care. Reports of alpaca reference intervals for one‐stage prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), concentration of fibrin degradation products (FDP), and antithrombin (AT) activities are scarce or nonexistent. Objective: The aim of this study was to determine values for blood coagulation times (PT, aPTT, and TT), FDP concentrations, and AT activities in healthy adult alpacas. Methods: Of blood samples collected from 35 clinically healthy adult alpacas via jugular venipuncture and placed into sodium citrate and FDP tubes, 29 samples were assayable for coagulation testing. PT, aPTT, and TT were determined by physical (mechanical) clot detection; AT activity was determined using a thrombin‐specific chromogenic substrate end‐point assay; and FDP concentrations were determined by the slide agglutination method. Results: Median values and ranges (minimum–maximum) were determined for PT (8.7 seconds, 6.6–11.2 seconds), aPTT (17.3 seconds, 11.9–22.5 seconds), TT (10.2 seconds, 5.4–16.0 seconds), and AT activity (123.3%, 104.8–144.2%). The mean concentration of FDP was <8 μg/mL. Conclusion: These values for coagulation times, FDP concentration, and AT activity will provide a useful starting point in the diagnostic evaluation of ill adult alpacas.     

Prothrombin time and activated partial thromboplastin time using a point‐of‐care analyser (Abaxis VSpro®) in Bennett's wallabies (Macropus rufogriseus)

There are few reports of coagulation times in marsupial species. Blood samples collected from 14 Bennett's wallabies (Macropus rufogriseus) under anaesthesia during routine health assessments were analysed for prothrombin time (PT) and activated partial thromboplastin time (aPTT) using a point‐of‐care analyser (POC) (Abaxis VSPro®). The wallabies had an aPTT mean of 78.09 s and median of 78.1 s. The PT for all wallabies was greater than 35 s, exceeding the longest time measured on the POC. Although PT was significantly longer, aPTT was similar to the manufacturer's domestic canine reference range.     

Overestimation of canine albumin concentration with the bromcresol green method in heparinized plasma samples

Albumin concentrations are routinely measured in dogs with bromcresol green (BCG)-binding assays on automated chemistry analyzers. Several variables affect this assay, including the length of reaction time, sample type, and lack of specificity of BCG for albumin. We observed that albumin concentrations measured with BCG appeared higher in heparinized plasma samples in sick dogs. The objective of this study was to determine the effect of anticoagulant and assay procedure on BCG albumin concentrations in clinically ill dogs. We hypothesized that albumin concentrations would be overestimated in heparinized plasma compared with serum because of the combination of heparin and fibrinogen. Furthermore, we hypothesized that the overestimation would be influenced by assay parameters. Blood was collected from 32 clinically ill dogs into tubes containing heparin, citrate, or no anticoagulant. Citrate was chosen to assess the effect of fibrinogen in the absence of heparin. Albumin concentration was measured in all 3 sample types from each dog using 2 different BCG procedures on an automated chemistry analyzer. The BCG procedures (standard and modified) differed in the wavelengths used for absorbance readings (standard, 600/700; modified, 570/505) and the time point at which absorbance was measured (standard, 100 seconds; modified, 40 seconds). In addition, the modified method incorporated a sample blank. Globulin fractions, fibrinogen concentration, and indices of lipemia, hemolysis, and icterus were evaluated for their contribution to the overestimation of albumin concentration in heparinized plasma compared with serum samples. Albumin concentrations were significantly higher (P 相似文献   

Evaluation of a bench-top coagulation analyzer for measurement of prothrombin time, activated partial thromboplastin time, and fibrinogen concentrations in healthy dogs

OBJECTIVE: To evaluate a bench-top coagulation analyzer for determination of prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen concentration in healthy dogs. ANIMALS: 55 healthy adult dogs. PROCEDURES: PT, APTT, and fibrinogen concentration were determined by use of the coagulation analyzer. Values were compared with results obtained independently by a conventional laboratory. RESULTS: Correlations (with 95% confidence intervals) between the coagulation analyzer and conventional laboratory values were 0.760 (0.610 to 0.857), 0.700 (0.448 to 0.721), and 0.896 (0.878 to 0.918) for PT, APTT, and fibrinogen concentration, respectively. Using linear regression, comparison of data from the coagulation analyzer and the conventional laboratory provided equations relating the coagulation analyzer values with values from the conventional laboratory and suggested that APTT and fibrinogen values from the coagulation analyzer and conventional laboratory were approximately the same within expected random variation. Prothrombin time values for the coagulation analyzer were significantly offset from the PT values for the conventional laboratory but still were correlated reasonably well with the conventional laboratory values. CONCLUSIONS AND CLINICAL RELEVANCE: By use of the mechanical method of analysis, fibrinogen concentrations obtained with a bench-top coagulation analyzer correlated well with results for a conventional laboratory, indicating that the coagulation analyzer is a reliable instrument for determination of this coagulation variable. Coagulation analyzer results for PT and APTT correlated less strongly with those for the conventional laboratory, but they would still be considered clinically reliable.     

Effect of reagent batch on activated partial thromboplastin time in canine plasma and use of the ratio system for standardization

In order to test the variability of the results of the activated partial thromboplastin time (APTT) in different reagent batches, 40 samples (20 from healthy dogs, 15 from patients with prolonged APTT as a result of different congenital or acquired haemostasis disorders, 5 from healthy dogs after in vitro addition of heparin) were used to compare 6 different lot Nos. of two commercial APTT-reagents (Pathromtin, PTT Reagent). Although the Friedman test showed a reagent batch dependency (p < 0.0001) for both reagents, only minor quantitative differences were observed with a variation coefficient of 2.7% (Pathromtin) and 2.4% (PTT Reagent), respectively. A second experiment was based on 105 samples measured with two batches of a third reagent (APTT-FS) with remarkable differences of results. Convergence of the results was achieved by converting into ratio values (quotient measurement value/control). However, statistical comparison still showed a significant difference. The study shows the good reproducibility of the APTT measured with different batches of the reagents Pathromtin and PTT Reagent in canine plasma, indicating that standardization is unnecessary. A standardization based on the ratio system can be used for reagents with a low batch consistency, requiring a high-quality control.     

Evaluation of a point-of-care coagulation analyzer for measurement of prothrombin time, activated partial thromboplastin time, and activated clotting time in dogs

OBJECTIVE: To evaluate a point-of-care coagulation analyzer (PCCA) in dogs with coagulopathies and healthy dogs. ANIMALS: 27 healthy and 32 diseased dogs with and without evidence of bleeding. PROCEDURE: Prothrombin time (PT), activated partial thromboplastin time (aPTT), and activated clotting time (ACT) were determined, using a PCCA and standard methods. RESULTS: Using the PCCA, mean (+/- SD) PT of citrated whole blood (CWB) from healthy dogs was 14.5+/-1.2 seconds, whereas PT of nonanticoagulated whole blood (NAWB) was 10.4+/-0.5 seconds. Activated partial thromboplastin time using CWB was 86.4+/-6.9 seconds, whereas aPTT was 71.2+/-6.7 seconds using NAWB. Reference ranges for PT and aPTT using CWB were 12.2 to 16.8 seconds and 72.5 to 100.3 seconds, respectively. Activated clotting time in NAWB was 71+/-11.8 seconds. Agreement with standard PT and aPTT methods using citrated plasma was good (overall agreement was 93% for PT and 87.5% for aPTT in CWB). Comparing CWB by the PCCA and conventional coagulation methods using citrated plasma, sensitivity and specificity were 85.7 and 95.5% for PT and 100 and 82.9% for aPTT, respectively. Overall agreement between the PCCA using NAWB and the clinical laboratory was 73% for PT and 88% for aPTT. Using NAWB for the PCCA and citrated plasma for conventional methods, sensitivity and specificity was 85.7 and 68.4% for PT and 86.7 and 88.9% for aPTT, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The PCCA detected intrinsic, extrinsic, and common pathway abnormalities in a similar fashion to clinical laboratory tests.     

Heparin in vitro sensitivity of the activated partial thromboplastin time in canine plasma depends on reagent.

The in vitro heparin sensitivity of 6 different commercial activated partial thromboplastin time (APTT) reagents was investigated based on artificial plasma samples prepared by addition of sodium heparin at different activities (0-1.5 IU/ml) to pooled normal canine plasma. Statistical analysis using 2-way analysis of variance was based on APTT ratios (APTT/mean APTT control). Significant differences between the APTT ratios of different APTT reagents (P < 0.00001) were found, which also depended on heparin activity (interaction between the factors; P < 0.00001). For example, mean APTT ratio at 0.7 IU/ml heparin varied between 1.2 and 2.5. The results of this study indicate that recommendations for the control of heparin therapy in dogs by APTT ratio should be reagent specific.     

Effect of sodium heparin and antithrombin III concentration on activated partial thromboplastin time in the dog

Regulation of blood coagulation was studied in 12 dogs, using subcutaneous administration of sodium heparin. Dosage of heparin needed to achieve the desired 1.5- to 2.5-fold increase in the activated partial thromboplastin time (APTT) was 250 to 500 IU/kg of body weight. Increased APTT lasted less than 6 hours. Repeated heparin administration, using the lowest dosage (250 IU/kg) every 6 hours, induced an unacceptable prolongation of clotting times during the first 2 days of treatment. Prolonged administration at a dosage of 200 IU/kg every 6 hours adequately maintained the desired hypocoagulative state initially; after 2 days, however, the prolonged APTT steadily decreased. The decreasing effect was proportionate to a decrease in plasma antithrombin III (AT III). To sustain a correctly balanced hypocoagulative state from prolonged subcutaneous administration of heparin, APTT values should be determined regularly to monitor therapy. In addition, transfusion of AT III-rich donor plasma may be necessary when low plasma AT III reduces the effects of heparin.     

Effects of storage time and freezing temperature on clinical chemical parameters from canine serum and heparinized plasma

To assess changes in 24 blood constituents in frozen serum and heparinized plasma, blood samples were drawn from 10 clinically normal German Shepherd army dogs. The storage characteristics of nine enzymes (ALP, ALT, amylase, AST, CK, GGT, GLDH, LDH, lipase), and 15 metabolites and minerals (albumin, bile acids, bilirubin, calcium, cholesterol, creatinine, fructosamine, glucose, magnesium, phosphate, potassium, protein, sodium, triglycerides, urea) were studied. Parallel samples of serum and heparinized plasma were stored for 90 and 240 days at two different storage temperatures, -200 degrees C and -700 degrees C. Sixteen of the 24 analytes (ALP, ALT, amylase, AST, CK, GGT, GLDH, LDH, bile acids, calcium, cholesterol, creatinine, fructosamine, magnesium, phosphate, urea) showed statistically significant (p < 0.05) changes during the storage period related to storage time, storage temperature, and sample type. Seven of the analytes (amylase, GGT, GLDH, LDH, bile acids, fructosamine, magnesium) showed changes of possible clinical importance with mean differences from baseline larger than 20% for the enzymes and 10% for the metabolites and minerals during the storage periods.     

Effects of 2 concentrations of sodium citrate on coagulation test results, von Willebrand factor concentration, and platelet function in dogs

BACKGROUND: Blood collection tubes containing 3.2% (0.109 M) sodium citrate, instead of 3.8% (0.129 M) sodium citrate, have recently become available in the United States. These tubes are visually indistinguishable from the traditional 3.8% sodium citrate tubes, except for wording on the label. Consequently, samples for hemostatic evaluation are frequently collected in tubes containing the lower concentration of sodium citrate. HYPOTHESIS: Results of hemostasis assays are different in samples collected in 3.2% versus 3.8% sodium citrate. ANIMALS: Twenty healthy dogs. METHODS: This study aimed at determining whether results of standard coagulation tests, von Willebrand factor concentration (vWF:Ag), and platelet function with the platelet function analyzer PFA-100a were affected by the different concentrations of sodium citrate. Blood samples were collected in tubes containing either 3.2% or 3.8% sodium citrate concentrations and processed routinely for coagulation assays (one-stage prothrombin time [OSPT], activated partial thromboplastin time [aPTT], fibrinogen concentration, and platelet count), vWF:Ag, and platelet function assays with a PFA-100. RESULTS: There was no significant difference between samples collected in 3.2% versus those collected in 3.8% sodium citrate for OSPT, aPTT, fibrinogen concentration, platelet count, or vWF:Ag. The closure times with collagen/adenosine diphosphate were significantly shorter (66 +/- 8.1 versus 74.8 +/- 9.7 seconds; P < .0001) with the 3.2% than with 3.8% sodium citrate concentration, and the hematocrit was significantly higher (47.9 +/- 5.6 versus 46.0 +/- 4.7 seconds; P = .03) in samples collected in 3.2% than in those collected in 3.8% sodium citrate. CONCLUSIONS AND CLINICAL IMPORTANCE: There is no clinically relevant effect of collection of blood into 3.2% or 3.8% sodium citrate.     

Effect of storage conditions on hemostatic parameters of canine plasma obtained for transfusion

OBJECTIVE: To evaluate the effects of various storage conditions on one-stage prothrombin time (OSPT), activated partial thromboplastin time (APTT), and fibrinogen concentration of canine plasma collected for transfusion. SAMPLE POPULATION: Plasma from 9 dogs. PROCEDURE: Whole blood was collected from dogs by means of jugular venipuncture and centrifuged at 7,300 X g for 20 minutes at 0 C. A plasma extractor was then used to generate plasma. Aliquots of plasma were collected in segments of plastic tubing and in microcentrifuge tubes, and plasma collection bags, tubing segments, and microcentrifuge tubes were immediately frozen at -30 C. Additional tubing segments and microcentrifuge tubes were stored at 2 C. After 1 week of storage, all samples were thawed, and OSPT, APTT, and fibrinogen concentration were measured. Collection bags and microcentrifuge tubes were refrozen at -30 C, and values were measured again 30 days after blood collection. RESULTS: Values for OSPT, APTT, and fibrinogen concentration did not vary significantly with storage time, temperature, or container. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that storage for up to 30 days and at 2 C versus -30 C did not have any significant effect on hemostatic parameters of canine plasma obtained for transfusion.