Comparison of an immuno-turbidometric method (STalia D-DI) with an established enzyme linked fluorescent assay (VIDAS) D-dimer for the exclusion of venous thromboembolism

The use of d-dimer tests for the exclusion of venous thromboembolism is an important advance in clinical practice and also has economic benefits. The Stalia D-Di (Diagnostica Stago, Asnieres, France) is a semi automated system for the quantification of d-dimer using an immuno-turbidometric method incorporating a suspension of latex microparticles coated with two different monoclonal antibodies specifically targeted against human d-dimer fragments. Results are available rapidly in <10 min compared with 35 min for the established VIDAS D-dimer automated enzyme-linked immunosorbent assay (ELISA, BioMerieux, Basingstoke, UK). During November and December 2005, 100 consecutive patients attending the outpatient deep venous thrombosis (DVT) clinic were tested using the VIDAS D-dimer as part of the routine DVT investigation. Using the same samples, D-dimer estimation was also performed on the STalia D-Di for comparison. Across a wide range of data (Vidas 83-5656) and (STali <200->4000), there was good agreement between the two methods. Using cutoff's of 500 microg/l fibrinogen equivalent units (Keeling et al., 1999), 42% (42/100) patients were negative (<500) and 46% (46/100) were positive (>500) on both systems. Six per cent (6/100) were positive on the Vidas but negative on the STalia and another 6% (6/100) were positive on the STalia but negative on the Vidas. In conclusion, 88% (88/100) of patients showed agreement and in the other 12% (12/100), one had a DVT as identified by Compression ultrasonography (CUS). In this study, there were seven patients with a DVT as identified by CUS and they all scored as 'likely' on a pretest clinical probability score and so negative D-dimer would not be used clinically to rule out the disease. The Vidas is a well established instrument for D-dimer measurement in outpatient DVT clinics, and in this small study the STalia compares very well and therefore would fit into an outpatient setting for D-dimer measurement. But ideally a larger study would be required before implementing new methodology in a clinical setting.     

Analytical performances of the D-dimer assay for the Immulite 2000 automated immunoassay analyser

We evaluated the analytical performances of a new commercial chemiluminescent enzyme immunometric assay for d-dimer measurement on the Immulite 2000 automated analyser. The within- and between-run coefficients of variations for low, intermediate and high d-dimer concentrations ranged from 2.2% to 5.1% and from 2.9% to 6.0% respectively. The assay was proven linear in a range of d-dimer concentrations comprised between 324 and 7602 ng/ml. Comparison of samples collected in either 0.109 mol/l sodium citrate or lithium-heparin tubes by Bland-Altman plots and nonparametric regression analysis (y = 0.858x - 39, r = 0.997; P < 0.0001) revealed a minimum bias, almost completely attributable to the dilution effect of the anticoagulant. Results of 56 outpatients' citrated plasma samples analysed with the Immulite 2000 d-dimer assay were compared with those of the current reference commercial immunoassay on the Mini Vidas Immunoanalyser. Although the nonparametric regression according to the method of Passing and Bablok and the relative Spearman's correlation coefficient was satisfactory (Immulite = 1.001 x Vidas - 181; r = 0.937, P < 0.001), some random discrepancies could be observed in Bland-Altman plots analysis. The analytical accuracy, calculated as the area under the Receiver Operating Characteristic (ROC) curve (AUC), was 0.961 (P < 0.0001). On the basis of the results of the present evaluation, we conclude that the analytical performances and the main technical features of new Immulite 2000 d-dimer assay make it a suitable method for the rapid quantification of d-dimer in clinical laboratories.     

Evaluation of an automated latex D‐dimer immunoassay in the clinical assessment of suspected venous thromboembolism

Because the reliability of clinical signs in venous thromboembolism (VTE) is poor, a highly sensitive, non‐invasive test may improve the selection of patients requiring further investigation. We assessed the sensitivity and negative predictive value of an automated D ‐dimer latex immunoassay (IL‐Test?) in 68 patients presenting with suspected VTE. The plasma D ‐dimer concentration was estimated and an appropriate diagnostic radiological investigation performed. Control values were obtained from healthy young and elderly volunteers. Using a cut‐off value of 330 ng/ml, the assay had a sensitivity of 100% and negative predictive value of 100% for VTE. We conclude that the IL‐Test^TM. automated D ‐dimer assay has a suitably high sensitivity and adequate negative predictive value to be included in a pre‐test clinical probability protocol for the evaluation of patients with suspected VTE.     

The use of a fixed high sensitivity to evaluate five D-dimer assays' ability to rule out deep venous thrombosis: a novel approach

Suspected deep venous thrombosis (DVT) is difficult to refute without complex diagnostic algorithms and expensive testing. We analysed five D-dimer assays' utility for exclusion of suspected DVT during a prospective clinical cohort trial, choosing a highly sensitive cut-off value at which to compare the assays. Assays were performed on 436 consecutive patients who were referred with symptoms that suggested a first episode of DVT. Venous thromboembolism (VTE) was defined as positive findings on comprehensive duplex ultrasonography or any episode, or complication of VTE detected during 3 months of clinical follow-up. All five assays were performed in 377 patients. At a highly sensitive cut-off value, all five assays reliably excluded DVT in the study population. While the choice of a highly sensitive cut-off value reduced the specificity of all the assays, the change in specificity differed between tests. Our findings suggest that a second-generation D-dimer assay could be used as a stand-alone test to rule out suspected DVT when a highly sensitive cut-off value is chosen. These findings should be subjected to a prospective management study, as a small reduction in sensitivity from our findings could result in a clinically relevant decrease in negative predictive value.     

Role of ELISA D-dimer test in patients with unstable angina pectoris presenting at the emergency department with a normal electrocardiogram

Patients with unstable angina pectoris and acute myocardial infarction have higher than normal D-dimer levels. The aim of the study was to determine the value of the D-dimer test in patients with unstable angina pectoris and a normal electrocardiogram on presentation at the emergency department. The study sample included 81 patients who met these criteria. Blood samples collected at admission were subjected to ELISA D-dimer. Findings were correlated with coronary risk factors, use of cardiac medications, blood levels of acute phase reactants (fibrinogen and C-reactive protein), cardiac enzymes levels, length of hospital stay, and catheterization findings. ELISA D-dimer levels were statistically significantly correlated with cardiac risk factors, namely male sex, older age, smoking, and hypertension (r = 0.25, P = 0.02; r = 0.43, P = 0.0001; r = 0.26, P = 0.03; r = 0.35, P = 0.002, respectively), in addition to use of cardiac medications (beta blockers, aspirin, nitrates), levels of acute phase reactants, length of stay, and catheterization findings. On multivariate analysis, only D-dimer level, age, and sex were predictors of length of stay (P = 0.018). The study suggests that D-dimer levels at admission to the emergency department may serve as an additional tool to predict the magnitude of unstable angina pectoris in patients with a normal electrocardiogram.     

Presenting D‐dimer and early symptom severity are independent predictors for post‐thrombotic syndrome following a first deep vein thrombosis

Post‐thrombotic syndrome (PTS) is the most common complication of deep vein thrombosis (DVT). Current preventative strategies are limited to the daily wear of graduated compression stockings (GCS). The aim of this study was to evaluate early predictors of PTS. One hundred and twenty‐two consecutive patients with a first DVT were prospectively recruited from diagnosis and followed for up to 6 months post‐end of anticoagulation. D‐dimer was measured in 107 participants at presentation and Villalta scale was evaluated in 70 participants at a median of 2 weeks following diagnosis. PTS developed in 51·6% of participants. GCS were obtained by 78·1% of participants, with 33·7% reporting daily wear at the end of follow‐up. Mean early Villalta scale was significantly higher in those with PTS (8·1 ± 3·7) compared to those without (2·6 ± 2·7, P < 0·001). Median D‐dimer was significantly higher in those with PTS [3260 ng/ml, interquartile range (IQR) 820–8000 ng/ml] compared to those without (1540 ng/ml, IQR 810–2520 ng/ml, P < 0·001). The adjusted odds ratio for every one point increase in early Villalta scale was 1·78 [95% confidence interval (CI), 1·19–2·64; P = 0·005] and for D‐dimer >1910 ng/ml it was 2·71 (95% CI, 1·05–7·03; P = 0·04). These markers could enable targeted counselling regarding GCS for those at high risk of PTS.     

ICSH Guideline for worldwide point-of-care testing in haematology with special reference to the complete blood count

These guidelines provide information on how to develop and manage a point-of-care (POCT) service so that reliable haematology results are produced regardless of where the test is performed. Many of the issues addressed here are relevant to POCT within hospitals or health centres; however, the principles are equally applicable to care in the community and doctors' offices. Other aspects discussed in this guideline are the initiation of the service (including indications for and limitations of a POCT service), staff training, type of haematology equipment selected, the blood results, monitoring of quality, accreditation, safety and cost. Equipment selected should generate results that are comparable to those of the local reference laboratory. If a complete independent evaluation of the POCT device has not been performed, the purchaser should perform a local assessment according to the protocol in this document. A literature search should also be undertaken to find independent peer reviewed evaluations on POCT equipment. Often the ideals discussed here may not be achievable in some developing countries but long-term training and education of POCT workers needs to be supported and constantly kept on government agendas to reach the recommendations advised here. Users should interpret these recommendations for their particular POCT needs and setting.     

Blood cell counting in neonates: a comparison between a low volume micromethod and the standard laboratory method

Background

Iatrogenic anaemia caused by repeated blood sampling to monitor laboratory parameters can contribute, particularly in neonates, to the need for transfusion. “Point of care” laboratory equipment uses smaller amounts of blood for analytic determinations and could, therefore, help to prevent secondary anaemia. In this study we compared the results of haematological parameters measured using a standard laboratory method and using a “point of care” micromethod, with the aim of validating the use of this latter method in clinical practice in neonatology.

Materials and methods

One hundred and fifty venous or capillary blood samples were taken from full-term or premature neonates 2–4 hours or 48 hours after birth. Each sample was processed by a standard haematology analyser and another micromethod instrument. Bland-Altman plots were constructed for each parameter and intra-class coefficients of correlation were calculated in order to evaluate the concordance between the two analysers.

Results

The concordance between the data obtained with the two analysers, expressed as the intra-class correlation, was 0.98 for white blood cell count, 0.97 for haemoglobin concentration, 0.96 for haematocrit, 0.95 for mean red cell volume and 0.98 for platelet count. The micromethod produced overestimated mean values for the leucocyte count (+1.27; p<0.001), haematocrit (+1.80; p<0.001) and platelet count (+13.55; p<0.001).

Conclusions

Overall, the concordance between the values obtained with the two analysers was high for each of the parameters taken into consideration. In the case of haemoglobin and leucocytes, give the high intra-class correlation and lack of systematic overestimation of one method over another, the micromethod guarantees a correct evaluation; however, despite the high intra-class correlations for platelet counts, the systemic error seems to suggest that the micromethod cannot guarantee an appropriate evaluation of this parameter.     

Accuracy and precision of hemoglobin point-of-care testing during major pediatric surgery

Introduction: The aim of the study was to compare accuracy and reproducibility of four point‐of‐care testing (POCT) devices (GEM^® Premier 3000, ABL 800 flex, GEM^®OPL^?, HemoCue^® B‐Hemoglobin) for hemoglobin (Hb) analyzes as compared with the reference laboratory method (Sysmex XE 2100) in children undergoing major surgery. Methods: Pediatric patients undergoing craniofacial, spine, hip, or cancer surgery were included. Blood samples for Hb testing were taken at several intraoperative time points and generally withdrawn from the arterial catheter, if accessible. Results: A total of 256 blood samples were taken intraoperatively from 71 pediatric patients. All POCT devices showed very small bias (maximum ?0.46 g/dL) to reference method as well as very good reproducibility (maximum coefficient of variation of 0.99%). However, in two cases (HemoCue), potential clinical relevant differences were observed beyond a range of 2 g/dL. Conclusion: All POCT devices tested and operated by trained staff for hemoglobinometry showed reliable test results. They all allow for simple, fast, and precise bedside determination of hemoglobin concentration in the intraoperative setting.     

缺血性中风患者测定血浆D—二聚体水平的意义

目的：探讨血浆D－二聚体水平与不同时相、不同面积缺血性中风患的关系。方法：采用胶乳凝聚法按不同年龄组分别测定92例正常人和118例缺血性中风患急性期和恢复期血浆中的D－二聚体含量。结果：缺血性中风患急性期及恢复期血浆D－二聚体的含量均较正常对照组明显升高（P＜0．001）,以急性期最高,恢复期D－二聚体含量已出现下降,与急性期相比有显性意义（P＜0．05）,但仍明显高于正常对照组（P＜0．05）。并且与梗死面积呈正相关;正常人D－二聚体含量随年龄的增高有增长的趋势,低年龄组与高年龄组有显性差异（P＜0．01）。结论：缺血性中风患急性期确实存在高凝状态,血浆D－二聚体水平不仅可作为观察缺血性中风病情轻重的指标,而且也是判断预后、观察治疗效果的监测指标之一。     

Diagnosis of deep vein thrombosis by plasma-soluble fibrin or D-dimer

The present study was designed to determine the cutoff values of D-dimer and soluble fibrin (SF) for the diagnosis of deep venous thrombosis (DVT) and pulmonary embolism (PE) in Japanese patients. Plasma levels of these molecules were measured in 243 patients suspected of having DVT and 100 healthy volunteers (controls). Out of 243 patients, 20 patients were diagnosed with DVT. In the control group, plasma levels of D-dimer and SF did not show normal distribution, and the 95% confidence intervals (CI) of D-dimer and SF were 2.45 microg/mL and 6.92 microg/mL, respectively. Plasma levels of D-dimer and SF of patients with DVT were significantly higher than of those without DVT. In patients with DVT, the minimum values of D-dimer and SF were 1.71 and 1.44 microg/mL, respectively. When the cutoff value was set at the average+1 SD of those of the control (D-dimer, about 1.8 microg/mL; SF, about 1.4 microg/mL), 1 and 0 patient with DVT was overlooked, respectively. The sensitivity and specificity of D-dimer and SF for DVT were 95% and 100%, and 61.9% and 53.8%, respectively. When the cutoff value was set at 95% CI of the control (D-dimer, 2.5 microg/mL; SF, 6.9 microg/mL), 2 and 9 patients with DVT were overlooked, respectively. The sensitivity and specificity of D-dimer and SF were 90% and 50%, and 77.6% and 88.3%, respectively. When the cutoff values set at 2.5 microg/mL of D-dimer or 6.9 microg/mL of SF, 1 DVT patient was overlooked, with sensitivity and specificity of 95% and 69.5%. Our data suggest that both D-dimer and SF are useful markers for the diagnosis of DVT and that measurement of both D-dimer and SF increases the sensitivity and specificity for the diagnosis of DVT/PE.     

High D-dimer levels at presentation in patients with venous thromboembolism is a marker of adverse clinical outcomes

Qualitative D-dimer results, together with clinical probability scores, are well established in the diagnosis of venous thromboembolism (VTE). The predictive value of quantitative D-dimer levels for various clinical outcomes in VTE patients is not fully understood. D-dimer levels obtained at presentation were analysed in 699 (360 men; 339 women) VTE patients for survival and occurrence of malignancy. Patients were followed for a median of 23 months. 17.2% patients had a D-dimer level >8000 ng FEU/mlat presentation, which was associated with decreased overall survival (OS) (P < 0.001) and event-free survival (EFS) (P < 0.001). 25.4% patients had malignancy and 4% subsequently developed malignancy following VTE. 29.9% of patients with VTE and malignancy had a D-dimer level >8 mg/l when compared with 13.4% of patients with VTE without malignancy (P < 0.001). 50% of patients who developed subsequent malignancy following VTE had a presentation D-dimer >8000 ng FEU/mlas compared with 13.3% of patients with VTE with out malignancy (P = 0.009). In conclusion, D-dimer >8000 ng FEU/ml at presentation in patients with VTE is a marker of poor OS, EFS and underlying malignancy. Consideration of screening for malignancy is recommended in patients with VTE with a presentation D-dimer >8000 ng FEU/ml and age >60 years.     

Determinants of ELISA D-dimer sensitivity for unstable angina pectoris as defined by coronary catheterization

Unstable angina pectoris is associated with elevated D-dimer levels. However, the operating characteristics (sensitivity, specificity, positive and negative predictive value) of the D-dimer assay for the diagnosis of coronary artery disease (CAD) are unknown. Using a prospective, observational design, we collected blood from 54 patients with unstable angina pectoris at admission and assayed for ELISA D-dimer levels. The sensitivity, specificity, and negative and positive prediction values for angiographically determined coronary artery disease were calculated at multiple discriminate levels. All patients underwent coronary catheterization. A statistically significant correlation was noted between ELISA D-dimer levels and age, male sex, hypertension, use of beta-blocker, fibrinogen levels and catheterization findings. No correlation was noted between ELISA D-dimer levels and degree of the coronary artery disease. Best results were provided at a discriminate level of 270 ng/ml, with sensitivity 70%, negative predictive value 72%, and overall accuracy 67%. All discriminate levels, however, provided values too low for diagnosis. In conclusion, ELISA D-dimer assay is a non-sensitive, non-specific test for coronary artery disease as defined by coronary catheterization. However, the assay adds information regarding the severity of disease in patients presenting with acute coronary syndrome.     

Quality assurance for point-of-care testing of oral anticoagulation: a large-scale evaluation of the Hemochron Junior Signature Microcoagulation System

We report the first large-scale evaluation of the Hemochron Junior Signature (HJS) Microcoagulation System for community monitoring of oral anticoagulation and establishment of a programme of internal and external quality assurance. Over 1600 HJS results, with a simultaneous venous sample for central analysis, were obtained over a 19 month period. Monitoring of an initial period of HJS results (n = 135) revealed an International Normalized Ratio (INR) over estimation (mean +1.05), with only 27% of results within 0.5 of the central laboratory INR. A correction factor was introduced which reduced the INR bias to +0.07 and improved the percentage of results within 0.5 of the central laboratory INR to 76% (n = 353). A revised correction factor was later introduced to adjust for an under estimation at higher INR values. This changed the INR bias to -0.05, with 76% of results within 0.5 of the central laboratory INR (n = 1174). Local external quality assurance samples were distributed monthly with a total of 791 samples during the study period. 84% of test results were within 15% of the median value (range 73-97% per month). These results emphasize the value of a robust quality assurance programme when using point-of-care devices for community monitoring of oral anticoagulation.     

Anticoagulation therapy in patients with venous thromboembolic disease

OBJECTIVE: To determine, in a representative sample of patients drawn from a variety of hospitals, the degree of adherence to consensus recommendations for anticoagulation among patients with deep vein thrombosis or pulmonary embolism. DESIGN: Cross-sectional review of a population-based random sample. SETTING: Twenty-one randomly selected Pennsylvania hospitals. PATIENTS: Of 357 randomly selected Medicare beneficiaries discharged from study hospitals with a diagnosis of deep venous thrombosis or pulmonary embolism during 1992, 43 charts were not reviewed for administrative reasons, 31 were miscoded or not treated with intravenous administration of heparin, and 13 were excluded for other reasons, leaving 270 in the final sample. MEASUREMENTS AND MAIN RESULTS: Overall, 179 patients (66%, 95% confidence interval [CI] 59%, 72%) received therapeutic anticoagulation (two consecutive partial thromboplastin times more than 1.5 times control) within 24 hours of starting heparin. Platelet counts were checked at least once during the first week of heparin therapy in 66% (95% CI 58%, 74%). At least 5 days of heparin therapy was given to 84% (95% CI 79%, 87%). Among 266 (99%) of the patients receiving warfarin, 193 (72%; 95% CI 63%, 80%) received heparin until the prothrombin time ratio or International Normalized Ratio was therapeutic. Patients who were started on warfarin therapy within 2 days of heparin had decreased length of stay (geometric mean 8.2 vs 9.7 days, p=.003). Compliance varied among hospitals. CONCLUSIONS: In a wide variety of hospitals, we found fair, but variable, compliance with consensus recommendations for anticoagulation of patients with venous thromboembolic disease. Simple interventions to improve compliance with these recommendations might improve quality of care and reduce costs. The analyses on which this publication is based were performed Under contract 500-96-P708, entitled “Utilization and Quality Peer Review Organization for the Commonwealth of Pennsylvania,” sponsored by the Health Care Financing Administration, Department of Health and Human Services. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government. The authors assume full responsibility for the accuracy and completeness of the ideas presented. This article is a direct result of the Health Care Quality Improvement Program initiated by the Health Care Financing Administration, which has encouraged identification of quality improvement projects derived from analysis of patterns of care, and therefore required no special funding on the part of this contractor. Ideas and contributions to the authors concerning experience in engaging with issues presented are welcomed.