The Effect of 3.2% and 3.8% Sodium Citrate on Specialized Coagulation Tests.
However, precise knowledge about their impact on specialized coagulation tests is lacking. Overwhelming amounts of studies were conducted with these 2 buffer concentration ranges. To provide comparative data, we conducted this observational study for estimating the effects on a broad panel of coagulation tests as well as on their reference value ranges.
MATERIALS AND METHODS
This prospective observational study was conducted at the Medical University of Vienna (Vienna, Austria) between September 2015 and July 2016. After we obtained written informed consent, 76 apparently healthy adult volunteers were included in the study. Volunteers undergoing therapy with anticoagulants (within the last 30 days) or with known coagulation disorders were excluded from participation. The study was approved by the local ethics committee (No. 404/2011) and was conducted in accordance with the 1964 Declaration of Helsinki (including current revisions). Blood samples were taken with 21-gauge needles in siliconized tubes (Vacuette, Greiner Bio-One, Kremsmiinster, Austria) prefilled with trisodium citrate (3.2% or 3.8%). After gentle tilting, the samples were centrifuged at 2500g for 15 minutes at 15[degrees]C (Hettich Mikro 220R, Tuttlingen, Germany). For assays of the lupus anticoagulant panel the samples were centrifuged a second time under the same conditions to obtain platelet-free citrate plasma. Coagulation analyses were performed either by using freshly drawn specimens or once-thawed aliquots stored below -70[degrees]C.
All analyses were executed under standardized conditions at the Department of Laboratory Medicine, which maintains a certified (according to ISO [International Organization for Standardization] 9001:2008) and accredited (according to ISO 15189:2008) quality management system. Using the same calibration settings, 3.2% and 3.8% buffered citrate samples were consecutively analyzed. Table 1 represents an overview of the analyzer platforms, reagents, calibrators, and controls used. The reagent-analyzer combinations were chosen with respect to measurement accuracy and validity, assays' robustness and practicability during the parameters' introduction phase at our laboratory. All assay procedures were performed according to the manufacturer's recommendations. Automatic multidilution procedures were applied for factor testing. The aPTT-LA (lupus-sensitive reagent) for lupus anticoagulant (LAC) confirmation testing was analyzed by using plasma with and without a reagent containing phosphatidylethanolamine. Lupus anticoagulant confirmation testing was considered positive when the difference between both aPTT-LA clotting times was greater than 8 seconds ([aPTT-LA.sub.Difference], Staclot LA [Diagnostica Stago S.A.S, Asnieres sur Seine, France]) or the ratio between the neat diluted Russell viper venom time (dRVVT) and the [dRVVT.sub.Confirm] ([dRVVT.sub.Ratio], Staclot DRVV Screen/Staclot DRVV Confirm) was greater than 1.25.
Numeric values are given as median with the interquartile range and are analyzed with the Wilcoxon rank sum test and the Spearman rank correlation test ([r.sub.[rho]]). The Passing-Bablok regression analysis was applied with bootstrapped confidence intervals. (11,12) To ensure linearity between 2 tested parameters, a CuSum test was applied. Further, Bland-Altman plots are used to assess agreement between the 2 methods (3.2% and 3.8% citrate) and scatterplots are applied to assess the linearity between the 2 methods. (13) To establish the reference interval, occurrence of Gaussian distribution (Shapiro-Wilk test) and the symmetry of skewness were assessed. Outliers were detected with the Tukey test. (14) If necessary, a logarithm transformation or a Box-Cox transformation was performed. (15) Reference intervals were calculated by using the robust method in accordance with the Clinical and Laboratory Standards Institute guideline C28-A3, (16) which uses a bootstrapping approach. Statistical significance was defined as P values less than .05 (2-tailed). Where appropriate, the Bonferroni-Holm method was applied to adjust for an error related to multiple testing. Data were statistically analyzed by using MedCalc Version 16.8.4 (Ostend, Belgium).
Among the 21 coagulation assays evaluated, the following 6 tests presented a significant prolongation or activity reduction when using 3.8% buffered citrate compared to 3.2% buffered citrate: aPTT-FS (factor-sensitive reagent containing ellagic acid); [dRVVT.sub.Confirm]; [dRVVT.sub.Ratio]; and activity levels of factor V, factor VIII, and protein C (Table 2). These parameters are graphically presented by using Bland-Altman plots (Figure 1, a through f) and their respective indicators of comparability are shown in Table 3. In Passing-Bablok regression analysis, a systemic and proportional difference was found in the aPTT-FS (Figure 2) with 3.80 intercept (0.24-7.49) and 0.86 slope (0.76-0.96). All other parameters with a significant difference did not show a systemic or proportional difference.
Lupus anticoagulant confirmation testing is based on calculated parameters and therefore potential measurement errors might be boosted. The [aPTT-LA.sub.Difference] indicated no significant difference between both citrate concentrations, using the Mann-Whitney U test. Passing-Bablok regression analysis was not applicable, since a significant deviation of linearity was found (Figure 3, a and b). However, the rank correlation coefficient was in a moderate range ([r.sub.[rho]] = 0.511), displaying a proportional difference between both citrate concentrations. In a next step, we sought to establish whether the use of different citrate concentrations led to any alterations of reference intervals. Most coagulation assays presented only minor differences in reference intervals between both citrate buffer concentrations (Table 4). Nonoverlapping 90% confidence intervals between 3.2% and 3.8% buffered citrate samples were found in the aPTT-FS. Lupus anticoagulant confirmation tests showed comparable reference range limits.
Despite the practical importance, limited comparative data are available for specialized coagulation test results measured with 3.2% and 3.8% buffered citrate samples. Most coagulation parameters tested showed good comparability between both citrate buffer concentrations. The aPTT-FS presented with a systematic and proportional deviation and therefore the citrate buffer concentration had a significant impact on this measurement. Further, the citrate buffer concentration significantly affected the upper reference range limit of the aPTT-FS. In comparison to the aPTT-A (activated partial thromboplastin time), a pronounced effect of the buffer concentration on the aPTT-FS was also found by Adcock et al. (6)
One might speculate that calculated coagulation parameters are more sensitive to alterations of the citrate buffer concentration, since 2 or more factors are used, each having a potential error itself. The [aPTT-LA.sub.Difference] presented only a moderate correlation, with a systemic difference between both citrate concentrations. Therefore, we advise special caution when comparing data of aPTT-LA confirmation testing. Interestingly, this effect was not seen in dRVVT confirmation testing. However, the [dRVVT.sub.Confirm] clotting time was considerably shortened in the higher citrate buffer concentration, contrary to expectations. In none of the cases tested was a false-positive result detected in either [dRVVT.sub.Ratio] or [aPTT-LA.sub.Difference] confirmatory testing. Furthermore, a statistically significant difference was found in [dRVVT.sub.Confirm], [dRVVT.sub.Ratio], factor V, factor VIII, and protein C activity, but their absolute difference was in a minor range and no deviation could be detected in regression analysis.
In the literature, there are several publications reporting a significant influence of the citrate concentration on the aPTT or PT, (6,7,17) but also publications that do not find any alteration in regard to the citrate concentration used. Apart from the parameter of inherent susceptibility to alterations of the citrate concentration, this might indicate that different reagent-analyzer combinations have different sensibilities in regard to the citrate concentrations used. (3,17,18) For 60 patients receiving oral anticoagulants, the relative difference of the PT between both buffer concentrations ranged from 3.7% to 20% when measured under similar conditions using different reagent-analyzer combinations. (17) Aside from the sodium concentration, the amount of magnesium or other electrolytes within the buffer might also have a significant influence on the comparability of parameters. (19,20) Along these lines, the tube brand has a statistically significant influence on the results of the PT or aPTT, as shown for 5 different tube brands containing 3.2% buffered citrate. (20,21)
In this evaluation, we assessed a broad spectrum of coagulation parameters by using a single specific reagent-analyzer combination for each parameter (Table 1). The reagent-analyzer combination itself might have an impact on the measurement, and therefore our results are not generalizable for other settings. (3,17,18) Since we evaluated healthy volunteers without any coagulation disorders or anticoagulant therapy, we are not able to estimate the potential difference in pathologic samples. The data regarding the influence of the citrate buffer concentration on monitoring anticoagulation are nebulous. Adcock et al (6) found in 5% of examined samples a significant deviation in INR (international normalized ratio) determination, due to different citrate buffer concentrations. Further, Payne et al (22) did not observe any statistically significant influence of the citrate concentration on low-molecular-weight heparin monitoring in patients with pulmonary embolism or deep vein thrombosis.
In conclusion, the alteration of 3.2% and 3.8% buffered sodium citrate on specialized coagulation tests in our setting was of limited relevance. As an exception, the aPTT-FS and [aPTT-LA.sub.Difference] were significantly affected by the citrate concentration used. Our findings demonstrate the comparability of data assessed with these citrate concentration ranges.
We extend our thanks to John Heath for his attentive proofreading of our manuscript.
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Franz Ratzinger, MD; Mona Lang; Sabine Belik; Klaus G. Schmetterer, MD, PhD; Helmuth Haslacher, MD; Thomas Perkmann, MD; Peter Quehenberger, MD
Accepted for publication October 23, 2017.
Published as an Early Online Release April 6, 2018.
From the Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria.
The authors have no relevant financial interest in the products or companies described in this article.
Corresponding author: Peter Quehenberger, MD, Department of Laboratory Medicine, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria (email: peter.quehenberger@ meduniwien.ac.at).
Caption: Figure 1. Bland-Altman plots of selected parameters using 3.2% and 3.8% citrate. a, aPTT-FS (ellagic acid containing activated partial thromboplastin time reagent). b, [dRVVT.sub.Confirm] (diluted Russell viper venom time confirmation testing). c, [dRVVT.sub.Ratio] (ratio between the neat dRVVT and the [dRVVT.sub.Confirm]). d, Factor V. e, Factor VIII. f, Protein C activity.
Caption: Figure 2. Scatterplot of the aPTT-FS using 3.2% and 3.8% citrate. Abbreviation: aPTT-FS, ellagic acid containing activated partial thromboplastin time reagent.
Caption: Figure 3. Graphical assessment of the [aPTT-LA.sub.Difference] using 3.2% and 3.8% citrate. a, Bland-Altman plot. b, Scatterplot. Abbreviations: aPTT-LA, activated partial thromboplastin time lupus-sensitive reagent; [aPTT-LA.sub.Difference], difference between clotting times of the aPTT-LA with and without a phosphatidylethanolamine-containing reagent.
Table 1. Overview of Methods Used for Assessment Method Unit Analyzer Prothrombin time s STA-R Evolution (a) Fibrinogen mg/dL (c) STA-R Evolution (a) aPTT-A s STA-R Evolution (a) aPTT-LA s STA-R Evolution (a) aPTT-FS s STA-R Evolution (a) dRVVT s STA-R Evolution (a) [dRVVT.sub.Confirm] s STA-R Evolution (a) [aPTT-LA.sub.Confirm] s MC10 PLUS (d) Antithrombin III % STA-R Evolutiona vWF-antigen % STA-R Evolutiona Factor II, factor V % Sysmex CA-7000 (b) Factor VII % Sysmex CA-7000 (b) Factor X % Sysmex CA-7000 (b) Factor Vlll/factor IX % Sysmex CA-7000 (b) Factor XI % Sysmex CA-7000 (b) Factor XII % Sysmex CA-7000 (b) Protein C activity % ACL-TOP (e) Protein S activity % STA-R Evolution (a) Protein S antigen % ACL-TOP (e) Method Reagents Prothrombin time Thromborel S (b) Fibrinogen STA-Liquid Fib (a) aPTT-A STA-aPTT (a) aPTT-LA PTT-LA (a) aPTT-FS Dade Actin FS aPTT (b) dRVVT Staclot DRVV Screen (a) [dRVVT.sub.Confirm] Staclot DRVV Confirm (a) [aPTT-LA.sub.Confirm] PTT-LA (with phospholipids) (a) Staclot LA Antithrombin III Stachrom ATIII (a) vWF-antigen Sta Liatest VWF Ag (a) Factor II, factor V Thromborel S (b), deficient plasma (b) Factor VII Thromborel S (b), deficient plasma (b) Factor X Thromborel S (b), deficient plasma (e) Factor Vlll/factor IX Dade Actin FS aPTT (b), deficient plasma (f) Factor XI Dade Actin FS aPTT (b), deficient plasma (b) Factor XII Dade Actin FS aPTT (b), deficient plasma (b) Protein C activity Biophen Protein C5 (g) Protein S activity Staclot Protein S (a) Protein S antigen Free Protein S (e) Method Calibrators Prothrombin time Standard Human Plasma (b) Fibrinogen NA aPTT-A NA aPTT-LA NA aPTT-FS NA dRVVT NA [dRVVT.sub.Confirm] NA [aPTT-LA.sub.Confirm] NA Antithrombin III STA Unicalibrator (a) vWF-antigen VWF-Ag Calibrator (a) Factor II, factor V STA Unicalibrator (a) Factor VII Standard Human Plasma (b) Factor X STA Unicalibrator (a) Factor Vlll/factor IX STA Unicalibrator (a) Factor XI STA Unicalibrator (a) Factor XII Standard Human Plasma (b) Protein C activity STA Unicalibrator (a) Protein S activity STA Unicalibrator (a) Protein S antigen HemosIL Calibration Plasma (e) Abbreviations: aPTT-A, activated partial thromboplastin time; aPTT-FS, ellagic acid containing activated partial thromboplastin time reagent; aPTT-LA, lupus-sensitive activated partial thromboplastin time; [aPTT-LA.sub.Confirm], lupus-sensitive activated partial thromboplastin time confirmation testing; dRVVT, diluted Russell viper venom time; [dRVVT.sub.Confirm], diluted Russell viper venom time confirmation testing; NA, not applicable; vWF, von Willebrand factor antigen. (a) Diagnostica Stago S.A.S, Asnietres sur Seine, France. (b) Siemens Healthcare GmbH, Erlangen, Germany. (c) Divide by 100 for g/L. (d) ABW Medizin und Technik GmbH, Lemgo, Germany. (e) Werfen, Barcelona, Spain. (f) Technolclone GmbH, Vienna, Austria. (g) Hyphen BioMed, Neuville-sur-Oise, France. Table 2. Synopsis of the Alteration Caused by the Citrate Buffer Concentration 3.2% Citrate 3.8% Citrate Parameter N Median (IQR) Median (IQR) PT 76 13.1 (0.7) 12.9 (0.8) Fibrinogen 78 266 (82) 260.5 (77) Antithrombin III 77 104 (9.3) 104 (9.5) vWF-antigen 73 95 (38) 93 (35.5) aPTT-A 78 34.5 (3.4) 34.6 (3.6) aPTT-FS 77 35 (2.7) 36.5 (3.6) aPTT-LA 79 38.2 (4) 37.9 (4.7) [aPTT-LA.sub.Confirm] 63 40.2 (4.3) 40.9 (4.4) [aPTT-LA.sub.Difference] 63 2.4 (2.7) 1.5 (2.7) dRVVT 70 42.6 (4.4) 43.3 (5.3) [dRVVT.sub.Confirm] 63 41.5 (3.5) 40.3 (4.4) [dRVVT.sub.Ratio] 62 1.04 (0.09) 1.06 (0.1) Factor II 76 110 (23) 110 (24) Factor V 76 115 (24) 112 (27) Factor VII 76 96 (29) 96 (27) Factor X 76 110 (26) 109 (27) Factor VIII 76 128 (64) 128 (61) Factor IX 76 113 (33) 112 (31) Factor XI 76 95 (20) 96 (18) Factor XII 76 112 (35) 111 (34) Protein C activity 75 101 (23) 100 (22) Protein S activity 73 108 (26) 110 (28) Protein S antigen 76 104 (29) 103 (27) Wilcoxon Correlation Parameter P Value (a) [r.sub.[rho]] PT .06 0.897 Fibrinogen .10 0.943 Antithrombin III .56 0.894 vWF-antigen .10 0.933 aPTT-A .16 0.921 aPTT-FS <.001 (b) 0.801 aPTT-LA .08 0.920 [aPTT-LA.sub.Confirm] .01 0.769 [aPTT-LA.sub.Difference] .09 0.515 dRVVT .02 0.864 [dRVVT.sub.Confirm] <.001 (b) 0.927 [dRVVT.sub.Ratio] <.001 (b) 0.714 Factor II .89 0.982 Factor V <.001 (b) 0.969 Factor VII .63 0.983 Factor X .82 0.917 Factor VIII <.001 (b) 0.973 Factor IX .02 0.975 Factor XI .40 0.933 Factor XII .12 0.984 Protein C activity <.001 (b) 0.978 Protein S activity .62 0.940 Protein S antigen .74 0.974 Passing-Bablok Regression Parameter Intercept Slope PT -1.00 (-16.00 to 8.40) 1.00 (0.90-1.17) Fibrinogen -2.44 (-14.96 to 9.89) 1.01 (0.97-1.07) Antithrombin III 0.00 (-10.20 to 9.45) 1.00 (0.90-1.10) vWF-antigen 2.03 (-1.69 to 6.09) 0.98 (0.94-1.03) aPTT-A 0.20 (-2.47 to 1.96) 1.00 (0.95-1.08) aPTT-FS 3.80 (0.24 to 7.49) 0.86 (0.76-0.96) aPTT-LA 1.71 (-1.50 to 4.69) 0.96 (0.88-1.04) [aPTT-LA.sub.Confirm] 2.26 (-5.11 to 8.60) 0.96 (0.80-1.14) [aPTT-LA.sub.Difference] Significant deviation from linearity dRVVT 3.76 (-1.37 to 8.29) 0.90 (0.79-1.03) [dRVVT.sub.Confirm] 1.99 (-1.83 to 5.61) 0.97 (0.88-1.07) [dRVVT.sub.Ratio] 0.02 (-0.19 to 0.21) 0.96 (0.77-1.11) Factor II 1.53 (0.00 to 7.07) 0.98 (0.93-1.00) Factor V -0.382 (-5.7 to 3.7) 0.97 (0.93-1.00) Factor VII 0.00 (-1.82 to 4.07) 1.00 (0.96-1.02) Factor X 0.00 (0.00 to 4.64) 1.00 (0.96-1.00) Factor VIII -0.95 (-6.37 to 4.02) 1.02 (0.99-1.07) Factor IX -2.41 (-10.44 to 3.53) 1.04 (0.97-1.11) Factor XI 0.00 (-4.99 to 5.29) 1.00 (0.95-1.05) Factor XII -0.77 (-4.87 to 0.00) 1.01 (1.00-1.05) Protein C activity 1.00 (-2.08 to 6.50) 1.00 (0.95-1.04) Protein S activity 1.60 (-6.94 to 10.30) 0.98 (0.90-1.06) Protein S antigen 0.80 (-3.21 to 3.71) 1.00 (0.97-1.04) Abbreviations: aPTT-A, activated partial thromboplastin time; aPTT-FS, ellagic acid containing activated partial thromboplastin time reagent; aPTT-LA, lupus sensitive activated partial thromboplastin time; [aPTT-LA.sub.Confirm], lupus sensitive activated partial thromboplastin time confirmation testing; [aPTT-LA.sub.Diference], lupus sensitive activated partial thromboplastin time confirmation testing difference; dRVVT, diluted Russell viper venom time; [dRVVT.sub.Confirm], diluted Russell viper venom time confirmation testing; [dRVVT.sub.Ratio], diluted Russell viper venom time confirmation testing ratio; IQR, interquartile range;PT, prothrombin time;vWF, von Willebrand factor antigen. (a) All P values are given 2-sided. (b) Statistical siginficance after Bonferroni-Holm correction. Table 3. Synopsis of Bland-Altman Plot Indices Mean ([+ or -] SD) Method Unit 3.2% Citrate aPTT-FS s 34.8 ([+ or -] 2.2) [dRVVT.sub.Confirm] s 41.2 ([+ or -] 2.7) [dRVVT.sub.Ratio] ... 1.04 ([+ or -] 0.08) Factor V % 113.4 ([+ or -] 19.5) Factor VIII % 142.0 ([+ or -] 45.8) Protein C activity % 103.1 ([+ or -] 16.4) Mean ([+ or -] SD) Method 3.8% Citrate Bias (95% CI) aPTT-FS 36.3 ([+ or -] 2.5) -1.5 (-1.8 to -1.2) [dRVVT.sub.Confirm] 40.4 ([+ or -] 2.8) 0.9 (0.6 to 1.1) [dRVVT.sub.Ratio] 1.07 ([+ or -] 0.08) -0.03 (-0.05 to -0.02) Factor V 110.9 ([+ or -] 18.3) 2.4 (1.2 to 3.7) Factor VIII 138.6 ([+ or -] 42.8) 3.4 (1.4 to 5.4) Protein C activity 101.6 ([+ or -] 16.6) 1.4 (0.7 to 2.2) Lower Limit of Upper Limit of Method Agreement (95% CI) Agreement (95% CI) aPTT-FS -4.0 (-4.6 to -3.5) 1.1 (0.6-1.6) [dRVVT.sub.Confirm] -1.1 (-1.6 to -0.7) 2.9 (2.4-3.3) [dRVVT.sub.Ratio] -0.14 (-0.17 to -0.12) 0.08 (0.06-0.10) Factor V -8.2 (-10.3 to -6.1) 13.1 (10.9-15.2) Factor VIII -13.6 (-17.1 to -10.2) 20.4 (17.0-23.8) Protein C activity -4.8 (-6.1 to -3.6) 7.7 (6.4-9.0) Abbreviations: aPTT-FS, ellagic acid containing activated partial thromboplastin time reagent; [dRVVT.sub.Confirm], diluted Russell viper venom time confirmation testing; [dRVVT.sub.Ratio], diluted Russell viper venom time confirmation testing ratio. Table 4. Reference Range (Lower and Upper Limit) of Assessed Parameters (a,b) Parameter N 3.2% Citrate 3.8% Citrate Prothrombin time 76 12.1 (12.0-12.3) 12.1 (11.9-12.2) 14.2 (13.9-14.3) 14.1 (13.8-14.2) Fibrinogen 78 162 (146-178) 164 (149-179) 375 (357-391) 368 (349-384) Antithrombin III 77 89 (87-92) 89 (87-91) 118 (116-121) 119 (116-121) vWF-antigen 73 57 (54-62) 56 (52-60) 176 (157-196) 178 (158-201) aPTT-A 78 29.5 (28.8-30.3) 29.5 (28.8-30.2) 39.4 (38.5-40.3) 39.4 (38.5-40.2) aPTT-FS 77 30.7 (29.9-31.5) 31.3 (30.5-32.1) 39.1 (38.5-39.8) 41.3 (40.5-42.1) aPTT-LA 79 32.8 (32.1-33.7) 32.1 (31.2-33.0) 44.0 (43.0-44.9) 44.3 (43.2-45.3) [aPTT-LA.sub.Confirm] 63 34.2 (33.1-35.5) 33.8 (32.7-35.0) 47.1 (45.9-48.4) 46.1 (45.0-47.1) [aPTT-LA.sub.Difference] 63 Not performed Not performed 6.6 (5.8-7.4) 6.2 (5.3-7.0) dRVVT 70 35.4 (34.3-36.6) 35.6 (34.4-36.8) 49.5 (48.2-50.8) 51.1 (49.7-52.3) [dRVVT.sub.Confirm] 63 35.9 (34.9-36.9) 34.9 (33.9-36.0) 46.9 (46.0-47.7) 46.2 (45.3-47.1) [dRVVT.sub.Ratio] 62 Not performed Not performed 1.18 (1.14-1.20) 1.22 (1.19-1.25) Factor II 76 80 (75-85) 79 (74-84) 143 (139-148) 142 (136-148) Factor V 76 76 (69-83) 75 (69-81) 151 (145-157) 148 (143-153) Factor VII 76 58 (51-64) 57 (50-63) 135 (128-142) 135 (128-142) Factor X 76 73 (66-79) 72 (65-79) 149 (142-155) 149 (142-155) Factor VIII 76 71 (65-79) 72 (65-79) 242 (214-269) 241 (216-265) Factor IX 76 75 (70-80) 75 (70-80) 169 (158-181) 163 (152-173) Factor XI 76 65 (60-70) 68 (64-73) 123 (118-129) 122 (118-127) Factor XII 76 63 (55-73) 66 (59-75) 157 (150-166) 154 (148-162) Protein C activity 75 75 (71-78) 72 (69-76) 136 (129-143) 137 (129-145) Protein S activity 73 66 (59-73) 65 (59-73) 153 (145-160) 153 (145-160) Protein S antigen 76 65 (59-71) 64 (59-71) 140 (135-145) 140 (135-146) Abbreviations: aPTT-A, activated partial thromboplastin time; aPTT-FS, ellagic acid containing activated partial thromboplastin time reagent; aPTT-LA, lupus-sensitive activated partial thromboplastin time; [aPTT-LA.sub.Confirm], lupus-sensitive activated partial thromboplastin time confirmation testing; [aPTT-LA.sub.Difference], lupus-sensitive activated partial thromboplastin time confirmation testing difference; dRVVT, diluted Russell viper venom time; [dRVVT.sub.Confirm], diluted Russell viper venom time confirmation testing; [dRVVT.sub.Ratio], diluted Russell viper venom time confirmation testing ratio; vWF, von Willebrand factor antigen. (a) Lower limit/upper limit. (b) Outliers were detected with the Tukey test.
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|Author:||Ratzinger, Franz; Lang, Mona; Belik, Sabine; Schmetterer, Klaus G.; Haslacher, Helmuth; Perkmann, Th|
|Publication:||Archives of Pathology & Laboratory Medicine|
|Date:||Aug 1, 2018|
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