Measurement of plasma fibrin D-dimer levels with the use of a monoclonal antibody coupled to latex beads

Recently, monoclonal antibody (DD-3B6) to fibrin D-dimer was prepared and coupled to latex beads to provide a specific test (Dimertest) for fibrinolysis. The purpose of this study was to evaluate the Dimertest assay as a clinical laboratory test for the measurement of plasma fibrin D-dimer derivatives. The Dimer-test assay specifically detected 2 micrograms/mL of purified fibrin D-dimer or fibrin D-dimer/fragment E complex added to afibrinogenemic plasma but did not detect 500 micrograms/mL of either fibrinogen fragments X, D, E, or 160 micrograms/mL cross-linked fibrinogen. The fibrin(ogen) degradation product (FDP) assays of American Dade or Wellcome Diagnostics detected 5.0 micrograms/mL of fibrin D-dimer and from 1 to 10 micrograms/mL of the other FDPs. Twenty-eight percent of 150 random plasma samples assayed from hospitalized patients were positive for fibrin D-dimer derivatives. Plasma samples from 152 patients suspected of having disseminated intravascular coagulation (DIC) were assayed for serum FDP (Wellcome Diagnostics) and plasma fibrin D-dimer derivatives. Samples from 69% of patients with serum FDP levels less than 10 micrograms/mL, and more than 90% of those with serum FDP levels greater than 10 micrograms/mL, were positive for fibrin D-dimer derivatives. Dimertest results were not modified by heparin, streptokinase, freeze-thawing, or clotting plasma. Serum fibrinogen-related antigens were immunoadsorbed from Dimer-test positive sera by anti-fibrinogen antibody and formalin-fixed Cowan I strain Staphylococcus aureus. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and protein blotting with the use of monoclonal antibody DD-3B6 demonstrated a protein band with similar mobility to purified D-dimer. The measurement of plasma fibrin D-dimer derivatives by the Dimertest assay is a rapid, sensitive, and specific laboratory test for fibrinolysis. The Dimertest assay has proven to be a useful addition to the clinical laboratory and should be helpful in the diagnosis and management of patients with diseases associated with fibrinolysis.     

Differentiation of fibrinolysis and fibrinogenolysis by analysis of FDP fragments]

We previously analysed the fragments of fibrin/fibrinogen degradation products (FDP) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) combined with immunoblotting. In this report, we studied the semi-quantitative analysis of fibrinolysis (degradation of cross-linked fibrin) and fibrinogenolysis (degradation of fibrinogen and/or unstable fibrin) of patients' samples by our method. In vitro study of FDP made it clear that an appearance of D fragment confirmed fibrinogenolysis and an appearance of DD fragment and/or high molecular weight fragments which have higher molecular weight than DY or X fragment confirmed fibrinolysis. In addition, a study with mixtures of various concentrations of fibrin degradation products (FbDP) and fibrinogen degradation products (FgDP) demonstrated a dose dependent intensity of band by immunoblot method. These results show that our method is favorable for the semi-quantitative analysis of fibrinolysis and fibrinogenolysis. We applied the method to 6 samples from patients with disseminated intravascular coagulation (DIC). Consequently, fibrinogenolysis was observed in all of 6 samples, in which fibrinogenolysis was more enhanced than fibrinolysis in one sample, and an equivalent degree of fibrinolysis and fibrinogenolysis were observed in 3 of 6 samples. Although our method was probably devoid of the ability to distinguish FgDP from degradation products of unstable fibrin, these findings indicate that fibrinogenolysis is, at any rate, enhanced in the majority of patients with DIC, besides fibrinolysis.     

Clinical significance of a new fibrinogen/fibrin degradation products(FDP) test using plasma samples for the diagnosis of fibrinogenolysis and fibrinolysis

Recently, a new fibrinogen/fibrin degradation products(FDP) test using monoclonal antibodies against FDP(LPIA FDP-P: FDP-P) has been developed, which is able to measure FDP directly in plasma. The objective of this study is to clarify clinical significance of the test in the diagnosis of fibrinogenolysis and fibrinolysis in comparison with a conventional FDP test using polyclonal antibodies against fibrinogen(FDP-S) and D-dimer test using monoclonal antibodies against D-dimer(D-D). The monoclonal antibodies used in FDP-P test was shown to recognize fragment X, Y and D1 derived from fibrinogen digested by urokinase, and was also to recognize XDP fragments, D-dimer and D derived from cross-linked fibrin digested by tissue plasminogen activator using SDS-PAGE and immunoblotting analysis. There was a good correlation of FDP levels between FDP-P test and FDP-S test. However, levels of FDP in both tests were discrepant in several samples. There was a tendency that the levels of FDP were higher in FDP-S test than in FDP-P test. Such discrepancy was suggesting that soluble fibrin monomer complex(FM) was recognized by the antibodies used in FDP-S test, but not recognized by the antibodies used in FDP-P test. There was also a good correlation of FDP levels between FDP-P test and D-D test. However, the levels of FDP in both tests were discrepant in several samples. The levels of FDP were higher in FDP-P test than in D-D test. These discrepant samples had lower levels of antiplasmin and higher levels of plasmin antiplasmin complex(PIC), and also showed XDP fragments, D-dimer, X, Y, and D1 by using SDS-PAGE. These observations suggest that D-D test measures only fibrinolytic fragments, while FDP-P test measures fibrinogenolytic fragments as well as fibrinolysis. In results, the FDP-P test was confirmed to be a useful tool to examine fibrinogenolysis as well as fibrinolysis more specifically than the conventional FDP test.     

Clinical usefulness of the measurement of plasma D-dimer levels

To evaluate the clinical usefulness of D-dimer, various effects on the measurement of D-dimer were examined. Although both fibrinolytic and fibrinogenolytic products were detected by the measurement of FDP, only fibrinolytic products were detected by the measurement of D-dimer. In patients with DIC and other thrombo-embolic diseases, plasma D-dimer levels were significantly higher than in normal persons. A significant positive correlation between plasma D-dimer and serum FDP was found in DIC patients. In patients with DIC associated with acute promyelocytic leukemia, which is thought to be an increased fibrinogenolysis state, serum FDP was higher than the plasma D-dimer which suggests that increased fibrinogenolysis affects the result of serum FDP measurement. Plasma D-dimer significantly increased 5 minutes after endoscopic embolization with thrombin in the patients with esophageal varices. However serum FDP increased 30 minutes after the treatment, which suggests that the D-dimer is more useful for rapid detection of coagulo-fibrinolytic change than serum FDP. Plasma D-dimer was significantly higher in patients with cerebral infarction and increased with age. These finding suggest the usefulness of plasma D-dimer measurement for the specific and rapid evaluation of coagulo-fibrinolytic activation and thrombo-embolic state.     

Studies on the fragments of FDP in 4 patients with DIC]

We previously studied fibrinolysis and fibrinogenolysis by analyzing fragments of fibrin/fibrinogen degradation products (FDP) employing sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. In this report, we characterized the fragments of FDP in four patients with disseminated intravascular coagulation (DIC), that were caused by various diseases. In the patients suffering from acute lymphoblastic leukemia (case 1) and acute suppurative cholangitis (case 3), DD and DY/X fragments resulting from fibrinolysis accounted for the most part of the FDP fragments. In case 3, D fragments resulting from fibrinogenolysis were also observed to much less extent. In a DIC associated with acute myeloblastic leukemia (case 2), both fibrinolysis and fibrinogenolysis were increased and resulted in high levels of D, Y and DY/X fragments, concomitant with moderate levels of DD and high molecular weight (HMW) fragments in the patient's sera. The increased fibrinogenolysis in this case was attributed to accelerated activation of plasmin. In a DIC patient of case 4, who underwent an operation due to hepatocellular carcinoma, marked increase in DY/X and HMW fragments and slight increase in DD fragment were observed on the day of operation. Hyperfibrinolysis documented in case 4 was explained by both increased production of thrombin and moderately accelerated activation of plasmin. Both qualitative and quantitative changes in the fragments of FDP during the courses of treatment in two cases of DIC were also noted. In summary, each underlying disease expresses characteristic pattern of FDP fragments in DIC.     

Measurement of plasma D-dimer for diagnosis of deep venous thrombosis

Venography was performed on fifty-six patients suspected of having deep venous thrombosis (DVT) of the legs. The accuracy of the D-dimer measurement in plasma using two latex tests and an enzyme-linked immunosorbent assay (ELISA) was compared with that of usual determination of total fibrin(ogen) degradation products (FDPs) in serum with respect to the presence of DVT. The three D-dimer tests were clearly superior to the FDP assay, but only the ELISA could accurately rule out the diagnosis of DVT with a predictive value of 100% when plasma D-dimer level was less than 200 micrograms/L. However, this test cannot be used for positive diagnosis (false positive rate of 69%). Thus, plasma D-dimer measurement with ELISA allows identification of patients in whom further investigation by means of more specific tests (venography or plethysmography) is indicated in order to establish the diagnosis of DVT. In contrast to this, sensitivity of the two latex tests studied was low (60 and 76%, respectively), which makes them unsuitable for emergency screening. In addition, the potential of D-dimer dosage for diagnosis of DVT in hospitalized patients is hampered by the presence of associated conditions that are responsible for elevated plasma levels in most cases.     

Incidence and possible reasons for discordant results between positive FDP and negative D-dimer latex assays in clinical specimens.

In general, FDP and D-dimer values have a correlation in clinical conditions associated with disseminated intravascular coagulation(DIC) or coagulation activation. However, there are some patients with discordant results who demonstrate elevated FDP and negative D-dimer results by latex agglutination assays. The incidence and possible reasons for the discordance between FDP and D-dimer results were investigated through simultaneous measurements (n = 763) from clinical patients with suspected DIC or coagulation activation. 24.8% (189/763) of samples with elevated FDP were negative for D-dimer assays by the latex agglutination method. Further detailed analysis on randomly-selected discordant samples (n = 41) revealed that the most common reason for the discordance was the lower sensitivity of the semiquantitative latex agglutination method for D-dimer, compared with quantitative enzyme or other latex immunoassay. The other contributing factors to the discordance were accelerated fibrinogenolysis without secondary fibrinolysis, elevated soluble fibrin monomer and rheumatoid factor.     

Clinical application of laboratory diagnosis: leukemia and DIC]

Plasma levels of molecular markers of hemostatic activation were investigated in 205 samples from patients with haematopoietic malignancies. These markers included thrombin/antithrombin III complex (TAT), D-dimer, plasmin/alpha 2plasmin inhibitor complex (PIC) and thrombomodulin (TM), and were assayed by EIA methods. Samples were divided into 4 groups according to the level of FDP: group A; FDP 10 greater than, group B; 10 less than or equal to less than 20 group C; 20 less than or equal to less than 40, and group D; less than 40. The mean level of each marker except TM increased in the order of group A, B, C and D. However, in many samples belonging to group A the plasma TAT or PIC levels and both were increased in spite of low FDP level. Furthermore, levels of TAT and PIC in several samples belonging to groups C and D were within the normal range. Also, the mean levels of each marker except TM increased in the order of 2, 3, 4, 5 and over 6 points in DIC score according to the criteria of DIC diagnosis by the research committee on DIC of the Ministry of Health and Welfare in Japan. Eight of the 11 samples (72.7%) obtained from cases with a DIC score of 3 points had high plasma levels of TAT, PIC and D-dimer. Plasma levels of these markers were increased after chemotherapy. These findings lead to the following conclusions: 1) FDP reflexed activation of coagulation and fibrinolysis, but 2) FDP was not more sensitive than TAT and PIC, and 3) the increase of FDP rarely resulted from fibrinogenolysis or non-plasmin mediated fibrinolysis. Furthermore, 4) TAT, D-dimer and PIC may serve as sensitive parameters of hemostatic activation in circulating blood and be valuable markers for early diagnosis of DIC.     

Fibrin monomer assay

Quantitative assay for fibrin monomer was done by use of a chromogenic substrate (S-2390, Coa set fibrin monomer). Samples from DIC prone patients with the underlying disease were assayed and classified into four groups. The pre DIC group showed higher FM values than the control with no laboratory coagulation abnormality, although the FDP . D-dimer showed no significant rise. FM assay is a useful marker for the detection of early coagulopathy in DIC. Administration of the AT III concentrate in the case of low level of plasma ATIII, thrombin . antithrombin complex I (TAT) caused a significant transient rise. The clinical course of DIC by TAT is often affected by the fluctuation of ATIII level in plasma, the usefulness of FM is that it reflects the real thrombin generation in DIC.     

An immunohistochemical study of experimental disseminated intravascular coagulation (DIC)

The experiment was focused on clarifying changes in fibrin or fibrinogen related materials (FRMs) in blood, urine, and renal tissues of rats with disseminated intravascular coagulation (DIC). DIC was induced by a continuous infusion of massive volume of physiologic saline (100 ml) immediately after endotoxin injection. FRM response was checked by biochemical and histochemical examinations at various intervals. In the blood of DIC rats, platelet and fibrinogen levels initially decreased, followed by an increasing plasma fibrin degradation products (FDP). Parallel with elevation of blood FDP the percentage of glomeruli with FRMs increased. Thereafter, FRMs were observed in renal tubuli and urine. Our observations indicated that FRMs in renal tubuli were derived from glomerular capillaries via Bowman's space. In conclusion, in DIC the immunoenzymehistochemical (IEH) procedure appeared necessary for an accurate pathological diagnosis, and the presence of FRMs in renal tubuli appeared to be an important finding even in absence of FRMs in glomeruli.     

Analysis of cross-linked fibrin and fibrinogen degradation products with SDS-PAGE and immunoblot

SDS-PAGE and immunoblot technique with anti-FDP-D, -FDP-E, -fibrinogen antibody or anti-FDP-DD monoclonal antibody were applied to analyze FDP fragments prepared from cross-linked fibrin and fibrinogen with plasmic digestion in vitro. FDP fragments of DY(260K), DD(187K), X(245K), Y(166K), D(77K, 97K), E1(58K), E2(46K) and E3(40K) were identified from data of molecular weight and reactivity to four antibodies referred to reports of other investigators. Serum FDP fragments from five DIC suspected patients were analyzed by the same methods. In two patients' sera, DD fragment was a main component, and in the other three patients' sera, D fragment was a main fraction. Proportions of high molecular weight fragments of FDP were considerably different in patients' sera. Appearance of D fragment in our cases was considered to be derived from unstable fibrin (fibrin monomer and dimer) rather than from fibrinogen. Molecular weight of DD fragments from patients' sera had heterogeneity (160 approximately 180K), and the values were different from that (187K) prepared from cross-linked fibrin. In conclusion, SDS-PAGE and immunoblot analysis of serum fragments of FDP will be an useful technique to investigate the clinical and pathological condition of DIC.     

AN IMMUNOHISTOCHEMICAL STUDY OF EXPERIMENTAL DISSEMINATED INTRAVASCULAR COAGULATION (DIC)

The experiment was focused on clarifying changes in fibrin or fibrinogen related materials (FRMs) in blood, urine, and renal tissues of rats with disseminated intravascular coagulation (DIC). DIC was induced by a continuous infusion of massive volume of physiologic saline (100 ml) immediately after endotoxin injection. FRM response was checked by biochemical and histo-chemical examinations at various intervals. In the blood of DIC rats, platelet and fibrinogen levels initially decreased, followed by an increasing plasma fibrin degradation products (FDP). Parallel with elevation of blood FDP the percentage of glomeruli with FRMs increased. Thereafter, FRMs were observed in renal tubuli and urine. Our observations indicated that FRMs in renal tubuli were derived from glomerular capillaries via Bowman's space. In conclusion, in DIC the immunoenzymehistochemical (IEH) procedure appeared necessary for an accurate pathological diagnosis, and the presence of FRMs in renal tubuli appeared to be an important finding even in absence of FRMs in glomeruli.     

Diagnostik der disseminierten intravasalen Gerinnung: Aussagekraft von löslichem Fibrin,D-Dimeren und Fibrin(ogen)-Spaltprodukten

Summary The validity of the fibrin(ogen) derivatives soluble fibrin, D-dimers and fibrin(ogen) degradation products was compared with other parameters in early and sensitive diagnosing of disseminated intravascular coagulation (DIC). In a clinical study 900 patients' samples from separate, defined groups were examined, including course observations of intensive care patients (n=38) and patients with acute pancreatitis. The fibrin(ogen) derivatives correlated very well with the degree of blood coagulation disturbances: in particular, D-dimers and soluble fibrin proved to be more sensitive in early diagnosis of DIC than other parameters. The SF-PS-turbidimetry demonstrated a good validity and practicality in the quantitative determination of soluble fibrin, but a suitable analyzer is essential. Determination of D-dimers is preferable to that of fibrin(ogen) degradation products (both in the latex-agglutination test) because of the better sensitivity and practicality; even more sensitive results were provided by the D-dimer-ELISA, which is, however, not practical in acute diagnostics. The decrease in protein C was at least equally sensitive as the antithrombin III-levels in indicating the consumption of the hemostatic potential. The decrease of thrombocyte counts and fibrinogen levels could first be detected in a later stage of DIC.In conclusion, D-dimers and soluble fibrin can improve the DIC diagnostics, making them more reliable; additionally, antithrombin III and possibly protein C deserve further consideration, although the fibrin(ogen) derivatives are apparently of greater importance.

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Abkürzungsverzeichnis ATIII Antithrombin III - DIC disseminierte intravasale Gerinnung - ELISA Enzyme-linked Immuno Sorbent Assay - FII, FV, FXIII Gerinnungsfaktor II, V, XIII - FDP Fibrin(ogen)-Spaltprodukte - FPA Fibrinopeptid A - LAT Latex-Agglutinationstest - PS Protaminsulfat - PTT partielle Thromboplastinzeit - tPA Gewebeplasminogen-Aktivator - TAT Thrombin-AntithrombinIII-Komplex - TPZ Thromboplastin-Zeit     

Criteria for diagnosing DIC

The differences between reagents of prothrombin time (PT), fibrinogen and fibrin and fibrinogen degradation products(FDP) were examined in patients with disseminated intravascular coagulation (DIC) and without DIC. The sensitivity of the PT ratio for DIC is lowered by the PT reagent with a high international sensitivity index, and the difference between PT reagents was marked. The sensitivity of PT-international normalized ratio (INR) for DIC was higher than that of the PT ratio and the difference between reagents in PT-INR was low. Though the difference between reagents for fibrinogen is slight, the usefulness in diagnosing DIC is also slight. Though the sensitivity of FDP for DIC was good, the difference between FDP reagents was marked. Therefore, standardization of PT and FDP seems to be necessary. Concordance of overt-DIC diagnostic criteria by the International Society of Thrombosis and Haemostasis (ISTH) and DIC diagnostic criteria of Japanese Ministry of Health and Welfare (JMHW) was about 70%, and overt-DIC diagnostic criteria of ISTH seemed to diagnose the typical type of DIC diagnosed by JMHW criteria. Finally, the diagnostic criteria of non-overt DIC are expected to become increasingly important.     

A novel molecular marker for thrombus formation and life prognosis--clinical usefulness of measurement of soluble fibrin monomer-fibrinogen complex (SF)

For a long time fibrinopeptide A(FPA), fibrinopeptide B(FPB), D-dimer, FM test, serum FDP, and thrombin anti-thrombin complex(TAT) are being used as molecular markers to for sure diagnose hypercoagulable state and thrombus formation. Indeed these molecular markers are very useful for diagnosing thrombus formation, disseminated intravascular coagulation(DIC), and the indicator of treatment of DIC. But these molecular parameters are not enough and difficult for prognosis of the disease or predicting the complication of patients as the most important subject for clinicians. The soluble fibrin monomer-fibrinogen complex (SF) is a complex coupling fibrin monomer and fibrinogen molecules to be formed in the early-activated state of blood coagulation. Thus such a molecular complex is expected to serve as a parameter for the diagnosis of thrombus formation and DIC, in particular its early stage. The aim of the present study is to evaluate a potential usefulness of a newly developed SF test utilizing an SF specific monoclonal antibody (IF-43). We measured SF together with established other parameters in 195 patients with DIC, subclinical DIC/hypercoagulable state, and non-DIC. The diagnosis of DIC was made based on a modified version of the criteria established by the Ministry of Health, Labor and Welfare of Japan. Underlying disease includes leukemia, malignant lymphoma, myelodysplastic syndrome (MDS), multiple injury, giant ovarian tumor, prostatic cancer with multiple bone metastasis, lung cancer, breast cancer with multiple lung and bone metastasis, severe pneumoniae, sepsis, hemophagocytic syndrome (HPS), and rheumatoid arthritis. The SF levels in DIC patients were significantly higher than those in the subclinical DIC/hypercoagulable state, and the non-DIC patients. Receiver operating characteristic (ROC) analysis shows that the specificity and sensitivity of the SF assay appears to be satisfactory. As the level of SF reflects the thrombin generation activity in plasma, it would serve as a strong tool to selectively kick up the state of thrombin generation. These results indicate that the SF could be a specific and reliable parameter for the diagnosis of DIC and contribute to legitimate managements of patients with DIC. The excessive life response to serious clinical insults, such as sepsis, severe pancreatitis, trauma and shock, is called systemic inflammatory response syndrome (SIRS). Once SIRS occurs, people may often die from serious complications such as adult respiratory distress syndrome (ARDS), acute lung injury (ALI), disseminated intravascular coagulation (DIC) and multiple organ failure (MOF). Especially, ALI followed by pneumoniae associated with SIRS could depend on patient's prognosis and life. That is to say, it seems to be urgent for clinicians to make differential diagnosis between Pneumoniae associated with SIRS and Coagulopathy (PASC) and Simple Pneumoniae (SP). Soluble fibrin monomer-fibrinogen complex(SF) is formed in the early-activated state of blood coagulation. Thus such a molecular complex is expected to serve as a parameter for the diagnosis of coagulopathy, in particular its early stage. The aim of the present study is to make differential diagnosis between Pneumoniae associated with SIRS and Coagulopathy (PASC) and Simple Pneumoniae(SP) by using a newly developed SF test utilizing an SF specific monoclonal antibody (IF-43). We measured SF together with established other parameters, hemogram, blood laboratory items in 7 patients with PASC and 17 patients with SP. The diagnosis of Pneumoniae was defined according to the criteria: clinical symptoms abnormal shadow in both Chest X-p and Chest CT, increased level of CRP, number of WBC. The diagnosis of SIRS was based on the criteria established by American College of Chest Physicians (ACCP)/Society of Critical Care Medicine (SCCM) Consensus Conference held in August of 1991 in Northbrook, IL (USA). Underlying disease includes leukemias, malignant lymphoma, myelodysplastic syndrome (MDS), multiple myeloma, idiopathic thrombocytopenia purpura(ITP), multiple injury (bone fracture), cerebral hemorrhage, enterocolitis, Appendicitis, lung cancer, larynx cancer, bronchiolitis obliterans organizing pneumonia(BOOP), chronic obstructive pulmonary disease(COPD), sepsis. The SF levels in PASC patients are significantly higher than those in SP patients (p < 0.001). Otherwise, there is no significant difference of the CRP levels between in PASC group and SP group (p < ns). There is no co-relationship between SF level and D-dimer level. Receiver operating characteristic (ROC) analysis shows that the specificity and sensitivity of the SF assay appears to be quite satisfactory. As the level of SF reflects the thrombin generation activity in plasma, it would serve as a strong tool to selectively kick up the state of thrombin generation. These results indicate that the SF could be a specific and reliable parameter for the diagnosis of PASC and contribute to legitimate managements of patients with PASC.     

Interpretation of hemostatic and fibrinolytic markers

Blood dose not normally coagulate in the blood vessels covered with endothelial cells, because these cells contain some substances responsible for antithrombotic action such as thrombomodulin, heparin-like substance, prostacyclin, nitric oxide and tissue plasminogen activator. Most important role of blood coagulation is hemostasis. Blood can coagulate in two ways: intrinsic coagulation pathway and extrinsic coagulation pathway that is activated by negatively charged substances and FVIIa-tissue-factor (TF) complex, respectively. Prothrombin time(PT) can represent extrinsic pathway, while activated partial thromboplastin time (APTT) can represent intrinsic pathway. PT is prolonged in such diseases as vitamin K deficiency, hepatic failure and warfarin intake, while APTT is prolonged such diseases as hemophilia A & B, von Willebrand disease and lupus anticoagulant. Cross mixing test is very useful to assess prolonged clotting time. FDP means fibrin/fibrinogen degradation products and D-dimer is the smallest products of fibrin degradation. These markers are often used to diagnose disseminated intravascular coagulation (DIC) and deep vein thrombosis (DVT). Thrombin-antithrombin complex (TAT) and plasmin-alpha2 plasmin inhibitor (PIC) can be used to evaluate the extent of coagulation and fibrinolysis activation, respectively. These two markers is essential for classify the pathophysiology of DIC: DIC with suppressed fibrinolysis, enhanced fibrinolysis or balanced fibrinolysis. In conclusion, exact interpretation of hemostatic and fibrinolytic markers is one of the most important abilities in clinical situation.     

False-positive D-dimer result in a patient with Castleman disease

In suspected cases of disseminated intravascular coagulation, concurrent elevation of both fibrin(ogen) degradation products (FDPs) and D-dimer levels aids in confirming the diagnosis. This pattern of results reflects the action of plasmin proteolysis of cross-linked fibrin polymers as well as fibrinogen. We report the case of a patient with human immunodeficiency virus (HIV) and Castleman disease who presented with a high-positive D-dimer level and a negative FDP level in the course of a workup for disseminated intravascular coagulation. This finding suggested the possibility of either a false-positive D-dimer or a false-negative FDP level. To investigate the former, a Western blot was performed on the patient's serum to determine the presence of the D-dimer. No D-dimer band was visualized on the Western blot, confirming the false-positive nature of the D-dimer result. Insufficient quantity of patient serum, however, prevented further investigation into the etiology of this result. The false-positive D-dimer result is likely attributable to interference caused by the patient's Castleman disease-associated monoclonal gammopathy, a phenomenon that has been reported in other immunoassays. As the development of lymphoproliferative disorders is especially common within the HIV population, and hypergammaglobulinemia in Castleman disease is particularly common, clinicians should be aware of this phenomenon when the laboratory findings do not fit the clinical picture. Although it is rare, recognition of potential paraprotein interference in immunoassays will help avoid undertreatment or overtreatment of patients based on erroneous laboratory results.     

D-dimer test: diagnostic role in clinical and sub-clinical DIC

D-dimer test is used as a diagnosis test for acute disseminated intravascular coagulation (DIC). This study was undertaken to find out its sensitivity and specificity in the diagnosis of acute DIC and its role in diagnosis of sub-clinical DIC, as there is limited data available on the subject. Of the 29 patients of clinically acute DIC, all had positive D-dimer test, and markedly prolonged PT, APTT and TT were seen in 24 (83%) of these patients. D-dimer test was found to be highly specific but less sensitive for the diagnosis of acute DIC. Of the 29 patients predisposed to sub-clinical DIC. D-dimer was positive is 26 (90%) patients and PT, APTT and TT were mildly prolonged in 11 patients. It is suggested that D-dimer positivity for the diagnoses of sub-clinical DIC need to be considered with caution and to be supplemented by other coagulation test including serial follow up with d-dimer and coagulation tests.     

Value of D-dimer measurement in the exclusion diagnosis of pulmonary embolism]

Diagnosis of pulmonary embolism, a common and potentially fatal disease, is first based on clinical probability assessment, and often requires invasive testing such as pulmonary angiography. However, it often represents a diagnosis challenge. The measurement of D-dimer, a specific fibrin degradation product, was recently introduced in the diagnosis strategy. Even if D-dimer levels are highly sensitive in the diagnosis of pulmonary embolism, they are not specific of an on-going venous thromboembolic process. Its high negative predictive value enables to validly exclude diagnosis of pulmonary embolism, particularly in outpatients, in the case of D-dimer levels below a well-defined cut-off value. Prospective management studies confirmed that D-dimer measurement could be validly used as an initial screening test in patients with clinically suspected pulmonary embolism. Using such a diagnosis strategy, imaging tests would be performed only in the case of high D-dimer levels i.e. above the cut-off level. Even if they constitute the gold standard, conventional Elisa are not useful as a routine emergency test. New rapid and automated assays based on various principles (Elisa-derived or micro-latex agglutination) are now available. All demonstrated both high sensitivity (about 100%) and negative predictive value (over 98%), using a well-defined cut-off level (usually defined to be 500 ng/mL). Finally, with the increasing number of new D-dimer assays currently available, a lack of standardization was pointed out. As the result, both the clinical significance and the cut-off level have to be defined in prospective clinical trials, for each individual assay.     

Monoclonal antibody to fibrin D-dimer (DD-3B6) recognizes an epitope on the gamma-chain of fragment D

Laboratory determination of fibrinolysis has been facilitated by diagnostic tests that use monoclonal antibody DD-3B6 to measure fibrin D-dimer levels in plasma. When DD-3B6 is reacted with soluble fibrin fragments, it is specific for fragment D-dimer. The authors have used immunoblot analysis of DD-3B6 binding to purified fragment D and fragment D-dimer to localize the binding site of the antibody. Although DD-3B6 recognizes only fragment D-dimer in solution, it binds to both immobilized fragment D-dimer and fragment D in immunoblots. When immunoblots were performed using protein which was electrophoresed under reducing conditions, DD-3B6 bound to the gamma-chain of fragments D1, D2, and D3. Therefore, the epitope recognized by DD-3B6 resides between amino acids 86 and 302 in the gamma-chain of fragment D. This epitope is masked in soluble non-cross-linked or nondegraded fibrin, but becomes expressed after cross-linked fibrin has been cleaved by plasmin.