Effects of factor VIII levels on the APTT and anti-Xa activity under a therapeutic dose of heparin.

In pregnant women, activated partial thromboplastin time (APTT) does not precisely reflect the anticoagulant effect of a therapeutic dose of heparin. However, the measurement of anti-Xa activity can be used to monitor the anticoagulant effect of heparin, since the plasma concentrations of coagulation factors increase in pregnant women. We evaluated the in vitro effects of increased concentrations of fibrinogen and other coagulation factors (FVII, FVIII, and FIX) on the results of assays of APTT and anti-Xa activity in plasma samples with various therapeutic concentrations of unfractionated heparin (UFH). In the presence of UFH, APTT was shortened by increased concentrations of fibrinogen, FVII, or FVIII, and this effect was much stronger when the FVIII concentration was increased. In the plasma samples containing 0.5 or 0.7 U/mL of UFH, the APTT was shortened by approximately half or one-third, respectively, when 6 U FVIII/mL was added to the sample. The anti-Xa activity was not influenced by increased concentrations of the coagulation factors. In the present study, we also evaluated the sensitivities to UHF of four APTT reagents, and found a 1.65-fold difference in the sensitivity to UFH among APTT reagents. Our results demonstrate that increased FVIII concentration shortens APTT under therapeutic doses of UFH, and that APTT thus underestimates the anticoagulant effect of UFH in pregnant women, mainly due to the increased FVIII concentration.

High-density lipoprotein levels have markedly increased over the past twenty years in Japan.

AIM: The high-density lipoprotein cholesterol(HDL-C) level is a major negative risk factor for atherosclerotic diseases dependent on various lifestyle parameters. Changes in the lifestyle of Japanese individuals over the past several decades is believed to have increased their total cholesterol levels and the incidence of cardiovascular disease in Japan. It is therefore important to assess the long-term trends in the HDL-C levels with respect to public health in the community. METHODS: In this study, accumulated data for the serum/plasma HDL-C levels published in cohort studies and obtained during health checkup programs in Japan were analyzed with respect to timedependent changes. RESULTS: The levels of HDL-C have continuously and significantly increased over the past 20 years by 12-15% according to the National Health and Nutrition Study, other cohort studies and commercially available data. On the other hand, the non-HDL-cholesterol levels demonstrated no changes or only a slight decrease during the same period. This finding is consistent with several sets of data obtained from health checkup programs. The commercially measured levels of serum apoA-I, an independent parameter of serum HDL, also showed a similar long-term increase, supporting the above findings. CONCLUSION: We concluded that the serum/plasma HDL concentrations in Japanese individuals, selectively, have increased continuously and significantly over the past 20 years or more. The reasons for this phenomenon and the consequent public health outcomes have yet to be investigated.

The Asian project for collaborative derivation of reference intervals: (2) results of non-standardized analytes and transference of reference intervals to the participating laboratories on the basis of cross-comparison of test results.

BACKGROUND: The 2009 Asian multicenter study for derivation of reference intervals (RIs) featured: 1) centralized measurements to exclude reagent-dependent variations; 2) inclusion of non-standardized analytes (hormones, tumor makers, etc.) in the target; and 3) cross-check of test results between the central and local laboratories. Transferability of centrally derived RIs for non-standardized analytes based on the cross-check was examined. METHODS: Forty non-standardized analytes were centrally measured in sera from 3541 reference individuals recruited by 63 laboratories. Forty-four laboratories collaborated in the cross-check study by locally measuring aliquots of sera from 9 to 73 volunteers (average 22.2). Linear relationships were obtained by the major-axis regression. Error in converting RIs using the regression line was expressed by the coefficient of variation of slope b [CV(b)]. CV(b) <10% was set as the cut-off value allowing the conversion. The significance of factors for partitioning RIs was determined similarly as in the first report. RESULTS: Significant sex-, age-, and region-related changes in test results were observed in 17, 15, and 11 of the 40 analytes, respectively. In the cross-comparison study, test results were not harmonized in the majority of immunologically measured analytes, but their average CV(b)s were <10% except for total protein, cystatin C, CA19-9, free thyroxine, and triiodothyronine. After conversion, 74% of centrally derived RIs were transferred to each local laboratory. CONCLUSIONS: Our results point to the feasibility of: 1) harmonizing test results across different laboratories; and 2) sharing centrally derived RIs of non-standardized analytes by means of comparative measurement of a set of commutable specimens.

[Establishment of a cut-off value for the diagnosis of acute myocardial infarction using a new CK-MB activity measurement reagent containing anti-MtCK antibody].

CK-MB is an important marker for the diagnosis of acute myocardial infarction (AMI). Since mitochondrial CK (MtCK) is universally present in the blood of healthy individuals, it is known to positively affect the measurement of CK-MB using the immunoinhibition method, causing false-positive results. We performed basic evaluation of ACCURAS AUTO CK-MB MtO, a new reagent containing anti-MtCK antibody that inhibits MtCK activity, and attempted to calculate a cut-off CK-MB level to diagnose AMI. The measurement was performed in samples submitted to the Clinical Laboratory of our center for the measurement of CK-MB. This method was confirmed to have satisfactory basic attributes concerning the reproducibility, linearity, lower detection limit, and effects of interfering substances. When 2886 samples were examined using this and conventional methods, the results of the two methods were correlated in some but not in others. In the samples that showed no correlation, MtCK was demonstrated by isozyme analysis using electrophoresis. The AUC calculated from the ROC curve in AMI patients was 0.912 with this method and 0.861 with the conventional method. The sensitivity and specificity of the new method were higher than those of the conventional method. The cut-off value determined by ROC analysis was 7.7 U/l using the new method and 13.6 U/l using the conventional method, causing an increase in false-positive results compared with the cut off value of 25 U/l widely used for the conventional method to date. However, the cut-off value for the new method that yielded a specificity comparable to 99.1%, which is the specificity of the conventional method using a cut-off value of 25 U/l, was 12 U/l. With a cut-off value of 12 U/l, the sensitivity was improved compared with that employing the conventional method, and both the sensitivity and specificity became comparable to those of the CK-MB mass method. This method is very useful for the accurate measurement of CK-MB activity.

Association of platelet aggregation with lipid levels in the Japanese population: the Suita study.

AIM: Platelets play a pivotal role in atherothrombotic diseases. Platelet aggregability induced by agonists has great interindividual variability; however, the factors influencing platelet aggregability variation have not been characterized in Asia. METHODS: To examine the confounding factors influencing platelet counts and responsiveness to agonists, we measured the platelet counts and platelet aggregability induced by 1.7 µM adenosine diphosphate (ADP) or 1.7 µg/mL collagen using a light transmittance aggregometer in the Japanese general population without medication or cardiovascular disease (387 men and 550 women) in the Suita Study. RESULTS: Platelet counts were negatively correlated with age in both men and women (Spearman's rank correlation coefficient: r(s)=-0.230 and -0.227; p< 0.01, respectively). In women, platelet counts were correlated negatively with the high-density lipoprotein (HDL) cholesterol level and positively with the low-density lipoprotein (LDL) cholesterol/HDL cholesterol (L/H) ratio (r(s)=-0.135 and 0.119; p< 0.01, respectively). In women, platelet aggregabilities by ADP and collagen were correlated with age (r(s)=0.118 and 0.143; p< 0.01, respectively), and collagen-induced platelet aggregability was correlated with the LDL cholesterol level, the L/H ratio, and the non-HDL cholesterol level (r(s)=0.167, 0.172, and 0.185; p< 0.01, respectively). Even after adjustment for age, systolic blood pressure, body mass index, and current smoking and drinking, the association of platelet counts with the L/H ratio in women and associations of collagen-induced platelet aggregability with the L/H ratio and the non-HDL cholesterol level remained. CONCLUSION: Examination of platelet counts and platelet aggregability induced by ADP and collagen revealed gender, age and lipid levels as factors influencing inter-individual variability.

Usefulness of antithrombin deficiency phenotypes for risk assessment of venous thromboembolism: type I deficiency as a strong risk factor for venous thromboembolism.

Inherited antithrombin deficiency, an established risk factor for venous thromboembolism (VTE), can be classified into type I (quantitative deficiency) or type II (qualitative deficiency). In the present study, we assessed the VTE risk associated with the phenotypes of antithrombin deficiency in patients admitted to our hospital. We found that patients with type I deficiency (n = 21) had more VTE events and earlier onset of VTE than those with type II deficiency (n = 10). The VTE-free survival analysis showed that the risk for VTE in patients with type I deficiency was sevenfold greater than that in patients with type II deficiency (hazard ratio: 7.3; 95% confidence interval: 1.9-12.2; P = 0.0009). The prevalence of type I deficiency in the VTE group (5.6%, 6/108) was higher than that in the general population (0.04%, 2/4,517) (odds ratio: 132.8; 95% confidence interval: 26.5-666.1; P < 0.0001). However, the prevalence of type II deficiency was not different between the VTE group and the general population. Our study indicated that the risk for VTE in patients with type I deficiency was much higher than that in patients with type II deficiency. Thus, simple phenotypic classification of antithrombin deficiency is useful for assessment of VTE risk in Japanese.