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J M Montoro

Publications and source records attributed to J M Montoro.

10 recordsLinked to original sources
PubMed2001

A comparison of FVII:C and FVIIa assays for the monitoring of recombinant factor VIIa treatment.

The use of recombinant factor VIIa (rFVIIa) is on the increase, not only to treat haemophilic patients with inhibitors, but also patients with other clotting disorders. However, the most appropriate method of monitoring this treatment remains a question that has yet to be resolved. We studied 24 plasma samples from patients receiving rFVIIa treatment (three had haemophilia A with inhibitors, and three a congenital FVII deficiency) and compared the results obtained from the FVII:C and FVIIa assays. Although a good correlation between the two methods was obtained (r = 0.91), the values of the FVII:C method were 1.63 higher than those of the FVIIa method, with a relatively wide margin in the interval of the FVII:C/FVIIa ratios obtained [95% confidence interval (CI) 1.38--1.88, range 0.68--3.68]. This interval became wider when we compared values of over 6 IU mL(-1), which led us to conclude that the two methods cannot be considered equivalent. As the FVIIa method specifically measures FVIIa, and FVII:C assay is known to have a wide interlaboratory variability, we believe that the FVIIa assay would be more suitable for the monitoring of rFVIIa treatment.

Antigens↗
PubMed2000

Influence of methylene blue photoinactivation treatment on coagulation factors from fresh frozen plasma, cryoprecipitates and cryosupernatants.

OBJECTIVE: To study the influence of virus photoinactivation with methylene blue (MB) on the coagulation factors of fresh frozen plasma (FFP) and the corresponding cryoprecipitates and cryosupernatants derived from it. MATERIALS AND METHODS: The photoinactivation procedure of the German Red Cross (Springe) was applied using Biomat (Grifols, Spain). Twenty isogroup pools of three plasma units were made from 60 U of FFP. The pools were split into three bags. One of them was photoinactivated, and pre- and postinactivation samples (MB-plasma) were obtained. The second bag was treated in the same way, followed by the preparation of MB-cryoprecipitate and MB-cryosupernatant. The third bag was not photoinactivated, and was processed in the same way to obtain control cryoprecipitate and cryosupernatant. The prothrombin time and activated partial thromboplastin time were analysed, as well as fibrinogen, factors (F) II, V, VII, VIII, IX, XI and XIII, antithrombin III, von Willebrand (vW) F:RCo, vWF:Ag and the multimeric structure of vWF. RESULTS: In plasma, the proteins most sensitive to photoinactivation were fibrinogen, FV, FVIII, FIX and FXI (24, 32, 28, 23 and 27% loss, respectively). In the MB-cryoprecipitate, the losses were higher for FVIII (23%), moderate for fibrinogen, FXIII and vWF:RCo (18, 14 and 13%, respectively) and minimal (only 3%) for vWF:Ag. In MB-cryosupernatants, the losses were higher for FV (26%) and moderate for fibrinogen (16%), FIX (18%) and FXI (19%), as well as for FII and FXIII (15%). The multimeric structure of vWF was not modified in MB-plasma or in MB-cryoprecipitates. The supernatants (both MB treated as well as controls) showed an absence of multimers of very high and high molecular weight. CONCLUSIONS: The quantitative and qualitative conservation of coagulation factors achieved in MB-plasma-derived products suggest that they are useful for the global replacement of coagulation factors and for deficiencies in FV and FXI. In countries lacking the economic resources to obtain virally inactivated concentrates, MB-cryoprecipitates could be useful in von Willebrand's disease and fibrinogen and FXIII deficiencies. MB-cryosupernatants could be employed in thrombotic thrombocytopenic purpura, in the correction of total or partial deficiencies of prothrombin complex factors and in specific deficiencies of FV and FXI.

Antiviral Agents↗
PubMed1999

Postoperative use of rFVIIa by continuous infusion in a haemophilic boy.

Continuous infusion of coagulation factor concentrates has proved to be safe and effective. Because rFVIIa (NovoSeven is a very expensive product and very frequent doses are needed, continuous infusion is expected to be highly cost-effective. The postoperative use of continuous infusion of rFVIIa in a haemophilic boy with a high titre FVIII inhibitor is reported. He presented with a large right knee haemarthrosis and was treated with intermittent doses of rFVIIa. After a transient improvement the haemarthrosis became worse and an open evacuation of the joint had to be made under treatment with bolus injections of rFVIIa for 3 days (120 microg kg(-1) every 2 h). A previous pharmacokinetic evaluation in this patient had showed that FVIIa recovery and half-life were less than expected. Continuous infusion of rFVIIa (20 microg kg(-1) h(-1)), with added low molecular heparin to prevent local thrombophlebitis, was started on the fourth postoperative day and maintained unchanged for 7 days. Four additional single bolus injections were given for early joint mobilization. The intervals between replacements of the pump syringes were progressively increased from 6 to 12 h and then up to 24 h. FVIIa plasma levels during continuous infusion ranged between 6.3 and 10.4 IU mL(-1). Although +FVIIa assays seemed to show good stability, we observed the formation of precipitates inside the syringes. The precipitates seemed to contain FVIIa. We concluded that FVIIa+ plasma levels of 6-10 IU mL(-1) were safe and effective to prevent postoperative haemorrhage in this patient. The addition of heparin to the rFVIIa concentrates, however, may cause precipitation and should be avoided. Individual pharmacokinetic evaluation may be useful to select the appropriate initial doses, especially in young patients.

Adolescent↗
PubMed1999

Factor VIII/von Willebrand factor complex in methylene blue-treated fresh plasma.

BACKGROUND: The effect of virus inactivation of fresh plasma with methylene blue has been studied on the factor VIII/von Willebrand factor molecular complex (FVIII/vWF), factor XIII, and fibrinogen. STUDY DESIGN AND METHODS: FVIII function or activity, vWF activity, vWF antigen, vWF:Ag, vWF multimeric structure, fibrinogen, and factor XIII were analyzed in paired samples of control fresh plasma (untreated) and the same fresh plasma treated with methylene blue. Treated plasma was filtered (0.8-1.2 microm), mixed with a methylene blue solution (300 microg/L), and illuminated at 50,000 lux for 30 minutes on both sides. RESULTS: Average loss of biologic activity of coagulation factors studied was 25 percent (FVIII function, 29%; fibrinogen, 39%; factor XIII, 16%; and vWF activity, 18%). Reduction in vWF activity was significantly lower than that in FVIII function (p<0.05), and the vWF multimeric structure did not show alterations. CONCLUSION: Methylene blue-treated plasma and the cryoprecipitates obtained from it may be effective for replacement therapy in cases of von Willebrand disease and deficiencies of factor XIII and fibrinogen, but the clinical studies are needed to verify that possibility.

Dimerization↗
PubMed1996

A modification of the APC resistance test and its application to the study of patients on coumarin therapy.

APC resistance appears to be caused, predominantly, by a mutation in coagulation factor V (nucleotide 1691: G to A). This phenomenon is usually studied by performing APTTs in the absence and presence of added APC. We studied a modification of the assay involving dilution of the test plasma in factor V deficient plasma, to render the assay more factor V specific. This modification was applied to 76 patients with venous thrombosis on coumarin treatment and to 45 controls. Two out of 45 controls (4.4%) showed abnormal results with the modified test. They also showed loss of factor V exon 10 Mnl I restriction site, associated to APC resistance. All remaining controls, with normal functional results by the modified assay, showed normal restriction profile. We detected 9 affected patients (11.8%), one of them homozygous or double heterozygous. In conclusion, the modified assay is very sensitive for factor V dependent APC resistance, and can successfully be applied to patients on coumarin therapy.

Adult↗
PubMed1989

[ELISA method for the determination of factor VII antigen].

The low plasma concentration of clotting factor VII makes it difficult to assay its antigenic fraction by the conventional methods of precipitation with specific antigens. Simple and peroxidase-conjugated antisera are currently available from commercial sources, thus allowing one to determine F VII:Ag by enzyme immunoassay. An ELISA method has been developed in this laboratory which provides sensitivity limits about 0.1% of the plasma concentration of F VII and correlates significantly with its functional activity (r = 0.603, n = 44, p less than 0.001). This technique can be highly helpful in characterising molecular variants of F VII, as well as in detecting acquired deficiencies of this factor.

Antigens↗
PubMed1989

[ELISA method using microplates developed with commercial antisera for measuring von Willebrand factor antigen].

The commercial availability of free and peroxidase-conjugated anti-FvW IgG fractions makes it possible to use ELISA methods for FvW: Ag determination in the routine blood coagulation laboratory. A highly sensitive microplate ELISA method was developed in our laboratory (capable of detecting 0.02% FvW: Ag), which proved to be reproducible, quick and not expensive. No significant differences were found between the results attained on different days in 4 control samples (variance analysis), variation coefficient about 12% being observed even for samples with only 11% FvW: Ag. The standard and control sample curves were parallel, which discarded a dilution effect in the assay. The correlation with Laurell's method was r = 0.889 (n = 34, p less than 0.001) and with ristocetin cofactor it was r = 0.677 (n = 19, p less than 0.005).

Antigens↗