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.     

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.     

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.     

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.     

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.     

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.     

Diagnosis of disseminated intravascular coagulation. Role of D-dimer

Detection of the cross-linked fibrin degradation fragment, D-dimer, in patients at risk for disseminated intravascular coagulation (DIC) is strong evidence for the diagnosis. D-dimer confirms that both thrombin generation and plasmin generation have occurred. Patients at risk for DIC (58) and normal controls (7) were studied. Thirty-three patients had DIC--with fragment D-dimer identified in their serum by immunoblotting. Latex agglutination measurements of fibrin(ogen) degradation products (FDPs) and D-dimer were compared with immunoblotting in the detection of D-dimer. FDP measurement was extremely sensitive but not specific. D-dimer measurement was less sensitive but highly specific. Used in tandem, screening with FDP and confirming with D-dimer, sensitivity and specificity were maximized, rendering a predictive value of a confirmed FDP of 100% in this cohort. D-dimer is a valuable adjunct for the laboratory diagnosis of DIC but is most appropriately used as a confirmatory test for the very sensitive FDP test.     

Serum FDP assay with latex photometric immunoassay and its analysis by immunoblotting

Sixty patients' sera with FDP-E value ranged from 200 to 2,500 ng/ml by LPIA system were assayed for FDP-Total (FDP-T) by the same system and FDP-DD by ELISA. Correlations of values between FDP-E, FDP-T and FDP-DD were excellent and ratio of FDP-T/FDP-E (T/E) and FDP-DD/FDP-E (DD/E) from same 60 sera were 32.4 + 7.4 and 1.55 + 0.50, respectively. Ratio of T/E from sera of FDP-E value demonstrating more than 500 ng/ml were classified into three groups, namely, 25.0-35.0, less than 18.0, and more than 50.0. Ten sera in each group were analyzed for FDP fragments of D, DD, Y, DY or X (DY/X) and high molecular weight (HMW) with SDS-PAGE and immunoblot method. It was found that relative concentration and proportion of D and DD.E fragments showed its characteristic pattern in each group.     

Comparison of a direct latex-agglutination technic with the tanned red cell hemagglutination inhibition immunoassay (TRCHII) for semiquantitation of fibrinogen/fibrin degradation products.

A new latex-agglutination kit for rapid screening for fibrinogen/fibrin degradation products (FDP/fdp) has been compared with a standard tanned red cell hemagglutination inhibition immunoassay (TRCHII). The latex-agglutination test results agreed with the TRCHII results for 489 of 588 samples (83%). FDP/fdp values were elevated by the latex-agglutination kit when normal by the TRCHII for 79 (13%) samples, and the reverse was true for 20 (3%) samples. Serial dilution of serum sample allowed reliable semiquantitation of FDP/fdp levels compared with TRCHII results (r=less than .001). The latex-agglutination test gave FDP/fdp values of larger than or equal to 10 mug. per ml. for sera from 11 of 13 patients who had acute pulmonary embolism and for only one of 24 normal control samples. The direct latex-agglutination kit for FDP/fdp appears to have appropriate sensitivity to serve as a screening test for acute pulmonary embolism in patients not receiving heparin therapy.     

The detection of fibrinogen/fibrin degradation products by means of a new antibody-coated latex particle

A rapid slide test for the detection of degradation products of fibrinogen/fibrin (FDP) using a new antibody-coated latex particle is described. The latex particle has been specifically coated with antibody to fragments D and E. The latex agglutination test (Thrombo-Wellcotest) has been compared with the tanned red cell haemagglutination inhibition immunoassay (TRCHII) in 143 patients with a variety of clinical conditions. There is a high degree of agreement between the methods with a coefficient of correlation of 0.83. The method provides a rapid, simple screening test for fibrin degradation products.     

Prevalence and clinical implications of heparin-associated false positive tests for serum fibrin(ogen) degradation products

An electrophoretic method has been applied to characterize specific fibrinogen and fibrin degradation products (FDP) in 135 serum samples from 59 consecutive patients having a positive latex agglutination test for serum FDP in the evaluation of consumption coagulopathy. In 20 of 135 positive samples, the principal fibrinogen derivatives present were not degradation products of fibrinogen or fibrin but were instead residual fibrinogen or fibrin monomer and polymers (FFMP) due to incomplete clotting. Heparin exposure was common in patients with positive FDP tests occurring in 29 of 59 patients (49%) with 81 of 135 samples (60%). Heparin exposure by parenteral administration or catheter was significantly correlated with a false positive serum FDP test because of residual FFMP occurring in 19 of 81 (23%) samples from heparin-exposed patients but in only 1 of 54 (2%) samples from patients without exposure (P less than 0.005). Treatment of the false positive samples with reptilase, an enzyme unaffected by heparin, resulted in complete removal of the residual FFMP, and in vitro experiments demonstrated that heparin-containing plasma samples could be completely clotted with either reptilase or protamine sulfate plus thrombin. Survey of 20 regional laboratories showed that only 10% used reptilase or protamine sulfate to prepare serum if heparin exposure had occurred and that this was done in only 22 of 5,049 (0.4%) of samples in the last calendar year. Greater attention should be given to proper preparation of serum from heparin-exposed patients, and physicians should be aware of the possibility of falsely positive or falsely elevated serum FDP tests in evaluation of consumption coagulopathy in heparin-exposed patients.     

Heparin reduction with the use of cardiotomy suction is associated with hyperfibrinolysis during distal aortic perfusion with a heparin-coated semi-closed cardiopulmonary bypass system

We sought to elucidate the effects of different anticoagulation levels and the use of cardiotomy suction on the postoperative coagulatory and fibrinolytic systems in patients undergoing distal aortic perfusion using a fully heparin-coated (semi-)closed cardiopulmonary bypass (CPB) system incorporating a soft reservoir bag. Thirty-two patients were divided into two groups: those who underwent cardiotomy suction (S group, 18 patients) and those who did not (N group, 14 patients). We administered 1–2 mg/kg heparin in the S group, which achieved an activated clotting time (ACT) of 345 ± 71 s. In the N group, we administered 0.7–1 mg/kg heparin, which achieved an ACT of 297 ± 52 s. Data on platelet counts and serum levels of fibrinogen, antithrombin III, D-dimer, and fibrin degradation products (FDP) were collected, and factors influencing these variables were analyzed by multiple regression analysis. Both the patient group and the initial ACT level were independent factors influencing postoperative levels of FDP and D-dimer, whereas peak ACT level and the use of selective visceral/renal shunt/perfusion, but not the patient group, were independent factors influencing the postoperative platelet counts. In the S group, a significant inverse correlation was found between the ACT and levels of FDP or D-dimer, whereas no correlation was found in the N group. The use of cardiotomy suction was associated with elevated FDP and D-dimer levels even when a fully heparin-coated semi-closed CPB system was used. Lower ACT levels with the use of cardiotomy suction were associated with higher FDP and D-dimer levels, whereas such a relationship did not exist when cardiotomy suction was not used.     

Significance of quantitative enzyme-linked immunosorbent assay (ELISA) results in evaluation of three ELISAs and Western blot tests for detection of antibodies to human immunodeficiency virus in a high-risk population.

The characteristics of primary (first) tests with three enzyme-linked immunosorbent assay (ELISA) kits for human immunodeficiency virus (HIV) antibody were determined. The three ELISAs were performed on 3,229, 3,130, and 685 specimens from high-risk individuals using the Litton (LT; Litton Bionetics Laboratory Products, Charleston, S.C.), Dupont (DP; E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.), and Genetic Systems (GS; Genetic Systems, Seattle, Wash.) kits, respectively. Evaluation was based on the distribution of quantitative test results (such as optical densities), a comparison with Western blot (WB) results, reproducibility of the tests, and identification of seroconverters. The performances of the GS and the DP kits were good by all four criteria and exceeded that of the LT kit. Primary ELISA-negative results were not always confirmed with repeat ELISA and by WB testing. The largest percentage of these unconfirmed negative test results came from samples with quantitative results in the fifth percentile nearest the cutoff. Thus, supplementary testing was indicated for samples with test results in this borderline negative range. Similarly, borderline positive primary ELISA results that were quantitatively nearest (fifth percentile) the cutoff value were more likely to be antibody negative on supplementary testing than samples with high antibody values. In this study, results of repeated tests by GS ELISA showed the least change from first test results. DP ELISA showed more unconfirmed primary positive test results, and LT ELISA showed more unconfirmed primary negative test results. Designation of a specimen with a single ELISA quantitative level near the cutoff value as positive or negative should be viewed with skepticism. A higher than normal proportion of specimens with high negative optical densities by GS ELISA (fifth percentile nearest the cutoff) and also negative by WB were found to be from individuals in the process of seroconversion.     

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.     

Interference by D-mannitol on serum D-arabinitol determination by enzymatic assay

We examined a disparity in D-arabinitol values between two commercial assay kits, LABOFIT and ARABINITEC-AUTO. The determined values by the former were increased by 26%(y = 0.2643x) because of concomitant D-mannitol, whereas those by our newly developed ARABINITEC-AUTO was increased only by 2%(y = 0.0242x). Of 109 samples, 5 samples were found to contain more than 100 mumol/l of D-mannitol. A clear relation(r = 0.89) was noted between the degree of disparity between measurements by the two methods and D-mannitol concentrations in samples. Thus, we have proved that the disparity is mainly caused by D-mannitol.     

肺炎衣原体感染与冠心病相互关系的研究

探讨肺炎衣原体(CP)感染与冠心病(CHD)的相互关系。应用ELISA法检测150例CHD患者及50名健康者(对照组)血清CP特异性抗体IgG,同时检测超灵敏C反应蛋白(hsCRP)、D二聚体(DDimer)及纤维蛋白降解物(FDP)。CHD患者血清检测结果:CP阳性率占72%;hsCRP阳性率占73%;DDimer、FDP指标在CP阳性组与CP阴性组比,P<0.05。实验证明,CP感染与CHD发病机理存在着一定的关系。     

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.     

Plasma factor VII levels in disseminated intravascular coagulation

To evaluate the activation of the extrinsic pathway of coagulation in disseminated intravascular coagulation (DIC), plasma factor VII coagulant activity (FVIIc) and antigen levels (FVIIag) were measured in 81 blood samples obtained from the 56 patients with DIC together with various hemostatic parameters. Plasma FVIIc (77 +/- 40%, range: 11-200%) and FVIIag (76 +/- 43%, range: 16-175%) were significantly lower in DIC subjects than in age-matched controls (FVIIc: 128 +/- 28%, FVII: 128 +/- 31%, p less than 0.01) and correlated significantly with both the antithrombin III and plasminogen activities (p less than 0.001). These results indicated that a decrease in factor VII levels is due to the consumption. However, there were several exceptions which showed elevated factor VII levels. This seems to be due to enhanced liver synthesis of factor VII compensating for the consumption. The level of tPA-PAI-I complex, a marker of pathologic endothelial stimulation, was negatively correlated with FVIIag (r = 0.45, p less than 0.05). Thus, the more the endothelium is pathologically stimulated, the more the extrinsic pathway is activated in DIC. The FVIIc/FVIIag ratio, an index of activation of factor VII zymogen, correlated with FDP and fibrin monomer levels (p less than 0.01). There were no correlations between the thrombin-antithrombin III complex. D-dimer, and alpha 2 antiplasmin-plasmin complex levels and factor VII levels. Considering the underlying diseases. the FVIIc and FVIIag levels were markedly lower in liver cirrhosis, but not significantly different in other diseases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tissue plasminogen activator and plasminogen activator inhibitor-1 levels in patients with acute paraquat intoxication

To investigate the effects of reactive oxygen species (ROS) on tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) plasma levels, and their possible implications on clinical outcome, we measured tPA and PAI-1 levels in 101 patients with acute paraquat (PQ) intoxication. The control group consisted of patients who ingested non-PQ pesticides during the same period. tPA and PAI-1 levels were higher in the PQ group than in the controls. PQ levels were significantly correlated with ingested amount, timelag to hospital, tPA level, and hospitalization duration. tPA levels were correlated with PAI-1, fibrin degradation product (FDP), and D-dimer. D-dimer levels were lower in the PQ group than in the controls. Univariate analysis indicated the following significant determinants of death: age, ingested amount, PQ level, timelag to hospital, serum creatinine, lipase, pH, pCO(2), HCO(3) (-), WBC, FDP, PAI-1, and tPA. However, multivariate analysis indicated that only PQ level was significant independent factor predicting death. In conclusion, tPA and PAI-1 levels were higher, while D-dimer levels were lower in the PQ group than in the controls, implying that ROS stimulate tPA and PAI-1, but PAI-1 activity overrides tPA activity in this setting. Decreased fibrinolytic activity appears to be one of the clinical characteristics of acute PQ intoxication.     

Antithrombin III assay using thrombin in disseminated intravascular coagulation (DIC), other thromboembolic disorders and hepatic diseases

Fifty cases comprising 11 cases of disseminated intravascular coagulation (DIC), 16 cases of venous thromboses and 23 cases of hepatic diseases were studied for AT III levels using clotting assay. Twelve samples were subjected to ATIII estimation by the commercially available synthetic chromogenic assay. Twenty age and sex matched controls were also analysed to find out the reference value for the techniques. Low AT III levels, if present, were correlated with other markers of DIC, viz FDP and D-dimer assays. There was a decrease in the AT III levels in all the three disease categories with a significant difference between the AT III levels of the three disease categories. In DIC, lowest levels were observed which correlated well with FDP and D-dimer levels. There was no significant difference between the average AT III levels measured by both the clotting and synthetic chromogenic assay with the former procedure being relatively inexpensive.