Plasma levels of von Willebrand factor antigen in acute bronchitis and in a normal population

Markers of vascular perturbation correlate with airway structural change in asthma

RATIONALE

Air trapping and ventilation defects on imaging are characteristics of asthma. Airway wall thickening occurs in asthma and is associated with increased bronchial vascularity and vascular permeability. Vascular endothelial cell products have not been explored as a surrogate to mark structural airway changes in asthma.

OBJECTIVES

Determine whether reporters of vascular endothelial cell perturbation correlate with airway imaging metrics in patients with asthma of varying severity.

METHODS

Plasma from Severe Asthma Research Program subjects was analyzed by ELISAs for soluble von Willebrand factor mature protein (VWF:Ag) and propeptide (VWFpp), P-selectin, and platelet factor 4. Additional subjects were analyzed over 48 hours after whole-lung antigen challenge. We calculated ventilation defect volume by hyperpolarized helium-3 magnetic resonance imaging and areas of low signal density by multidetector computed tomography (less than -856 Hounsfield units [HU] at functional residual capacity and -950 HU at total lung capacity [TLC]).

MEASUREMENTS AND MAIN RESULTS

VWFpp and VWFpp/Ag ratio correlated with and predicted greater percentage defect volume on hyperpolarized helium-3 magnetic resonance imaging. P-selectin correlated with and predicted greater area of low density on chest multidetector computed tomography less than -950 HU at TLC. Platelet factor 4 did not correlate. Following whole-lung antigen challenge, variation in VWFpp, VWFpp/Ag, and P-selectin among time-points was less than that among subjects, indicating stability and repeatability of the measurements.

CONCLUSIONS

Plasma VWFpp and P-selectin may be useful as surrogates of functional and structural defects that are evident on imaging. The results raise important questions about why VWFpp and P-selectin are associated specifically with different imaging abnormalities.

Microalbuminuria, von Willebrand factor and fibrinogen levels as markers of the severity in COPD exacerbation

In COPD, the systemic effects of the disease reflect the structural and/or biochemical alterations occurring in the structures or organs other than the lungs in relation to the characteristics of the primary disease. The disorders of endothelial structures due to COPD may lead vascular pathologies, such as ischemic heart disease, stroke, to occur more commonly in those with COPD. On consideration of the fact that the vascular endothelium is a major site in which the systemic effect of the inflammation occurs, should von Willebrand Factor, a clotting factor of endothelium origin, and the plasma level of fibrinogen vary with the severity of the disease in COPD, the variability of arterial blood gas values, and the stability or exacerbation of the disease? Considering the fact that microalbuminuria is an indirect manifestation of the renal endothelial permeability and/or renal perfusion; should there be an association between microalbuminuria and the severity of COPD? Therefore, in order to assess the effect of the systemic inflammation in COPD on the vascular endothelium, we compared the levels of the plasma vWF, fibrinogen, 24-h urine microalbuminuria of those with stable COPD (33 patients) and exacerbation of COPD (26 patients) with those of the controls (16 healthy subjects). The mean age was 63.42 -/+ 10.29, 68.00 -/+ 9.77 and 59.63 -/+ 14.10 years in SCOPD, COPDAE, and CG, respectively. The level of microalbuminuria was found to increase significantly in COPDAE group, compared to that of the controls (P = 0.004). When we investigated the relation between smoking burden and microalbuminuria, vWF, fibrinogen levels, the amount of consumption and positive relationship were found significant. (r = 0.336, P = 0.003 between smoking pack-years and vWF, r = 0.403, P = 0.001 between smoking pack-years and fibrinogen, and r = 0.262, P = 0.02 between smoking pack-years and microalbuminuria). The levels of vWF and fibrinogen are AECOPD > SCOPD > CG, with the highest being in AECOPD, and the difference among the groups was statistically significant. The relationship between the level of hypoxemia and microalbuminuria, fibrinogen and vWF was found to be significant (r = -0.360, P = 0.005 between oxygen saturation and microalbuminuria, r = -0.359, P = 0.005 between the level of PaO(2) and fibrinogen, and r = -0.336, P = 0.009 between PaO(2) and vWF). In conclusion, the levels of plasma vWF, fibrinogen, and microalbuminuria may be helpful in grading the severity of COPD exacerbation. The related increase in these markers may represent a possible pathophysiological mechanism behind the increased vascular morbidity of patients with COPD and detecting indirectly the endothelial dysfunction as a manifestation of systemic outcomes due to COPD and in detecting earlier the cases in which the risk for developing the associated complications are higher. We suggest that further studies are necessary to investigate the impact of antithrombotic treatment on microalbuminuria, plasma vWF and fibrinogen as markers of endothelial dysfunction coexisting COPD exacerbation.

The significance of evaluating conventional inflammatory markers in Von Willebrand factor measurement

BACKGROUND

The appropriate clinical interpretation of Von Willebrand factor (VWF) measurements is crucial since inherited or acquired deficiencies are responsible for a potentially life threatening bleeding disorder, whereas increased plasma concentrations may be associated with an increased thrombotic risk. Besides age and blood group, the variability introduced by the presence of an acute phase response might contribute to decrease the clinical usefulness of this measurement.

METHODS

To investigate the relationship between conventional inflammatory markers and VWF, 387 consecutive unselected patients undergoing surgical procedures at our University Hospital were systematically investigated for routine laboratory testing, including also VWF Antigen (VWF:Ag), C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) as parts of a routine preoperative screening program.

RESULTS

After stratifying the study population according to the upper limit of the reference range of the two inflammatory markers, a significantly increased median VWF:Ag plasma concentration was observed for subjects with increased value of both CRP (CRP>5 mg/L=VWF:Ag>120 UI/dL; CRP<5 mg/L=VWF:Ag 98 UI/dL, p=0.003) and ESR (ESR>30 mm/hg=VWF:Ag>120 UI/dL; ESR<30 mm/hg=VWF:Ag 96 UI/dL, p<0.001). A significantly different frequency distribution of VWF:Ag concentrations was also observed in subjects with values of inflammatory markers above the upper limits of the reference ranges when compared to those with normal values. In particular, the prevalence of subjects with VWF:Ag levels>120 UI/dL was six- and nearly three-times higher in subjects with abnormal values of CRP (55.8% versus 9.3%, p<0.001) and ESR (54.5% versus 18.7%, p<0.001), respectively.

CONCLUSIONS

Results of this investigation demonstrate that the evaluation of conventional inflammatory markers would represent a valuable tool to enhance the clinical usefulness of VWF measurements, especially in patients with transitory and subclinical inflammation. Since VWF and factor VIII are likely to increase in parallel, we suggest that their measurements should be repeated at least after 6 months to one year in the presence of concomitantly increased values of inflammatory markers, such as ESR and/or CRP.

In vitro bleeding test with PFA-100-aspects of controlling individual acetylsalicylic acid induced platelet inhibition in patients with cardiovascular disease

OBJECTIVES

This study investigated the usefulness and practicability of a platelet function analyzer (PFA-100(TM), DADE-Behring, Germany) to determine individual platelet inhibition in patients treated with acetylsalicylic acid (ASA).

BACKGROUND

Patients with coronary artery disease (CAD) routinely and during angioplasty (PTCA) receive standard doses of ASA to avoid acute coronary syndromes and abrupt vessel closures without information of the individual efficacy of platelet inhibition.

METHODS

With the PFA-100(TM) a standardized bleeding time is measured. Whole-blood anticoagulated with 3.2% sodium citrate is aspirated through a capillary ( solidus in circle 200 microm) and through an aperture ( solidus in circle 147 microm). The time until occlusion of the aperture (closure time, CT) by a stable platelet plug induced by shear stress, collagen and epinephrine (COLL/EPI-CT) or shear stress, collagen and adenosine 5'-diphosphate (COLL/ADP-CT) is determined. To examine the usefulness of the PFA-100(TM) as a rapid bedside test and the individual effect of ASA, closure time was measured in healthy individuals (n=17), in patients with stable CAD (n=19) and in patients undergoing PTCA (n=8).

RESULTS

Patients with stable CAD and regular medication with 100 mg ASA per day for at least 3 month showed shorter COLL/ADP-CT in comparison to healthy individuals who took only one single dose of 100 mg ASA. Of the patients with CAD 63% had a COLL/EPI-CT within normal range suggesting a low or no response to ASA. Also only 50% of the patients undergoing PTCA reached the expected COLL/EPI-CT>300 s after an additive single dose of 500 mg ASA intravenously. Neither heparin, phenprocoumon, sex nor different blood sampling methods seem to influence the measurements relevantly.

CONCLUSIONS

This pilot study indicates that with the PFA-100(TM) test device a simple and quick measurement of an in vitro bleeding time is possible. It is able to detect an increase in the bleeding time after a single dose of ASA 100 mg in healthy subjects, reflecting a sensitive detection of ASA induced changes in platelet inhibition respective activation. Differences in the individual response to ASA could be observed in healthy subjects, patients with stable CAD and patients undergoing PTCA. Further studies should validate the PFA-100(TM) with standard methods to determine ASA response in patients with cardiovascular disease and investigate implications for treatment and outcome in this patient group.

Chronic respiratory symptoms, von Willebrand factor and longitudinal decline in FEV1

Although some risk factors for accelerated decline in forced expiratory volume in 1 s (FEV1) such as cigarette smoking, are well defined, it is not possible to identify those individuals with the most rapid rates of decline. Von Willebrand factor (vWF) is a product of both the pulmonary and systemic endothelium, and serum levels are raised during episodes of acute bronchitis. We hypothesized that raised serum levels of vWF may indicate sub-clinical pulmonary injury and so may predict subsequent accelerated decline in FEV1. The aims of this study were 1. to define the prevalence of chronic respiratory symptoms and obstructive airway disease in an inner-city British population and 2. to determine whether elevated levels of von Willebrand factor (vWF) identify those individuals at risk for more rapid decline in FEV1 over time. In 1987, all 2013 individuals aged 45 to 74 years at an inner-city general practice were mailed a respiratory symptom questionnaire. One in six of the responders were asked to attend for spirometry and for assessment of serum vWF. In 1996, those individuals who had spirometry and vWF assessed in 1987 were traced, and repeat spirometry was performed. In 1987, 1527 of 2013 (75.8%) individuals completed the questionnaire. Forty-two point two percent of responders reported shortness of breath on hills, 34.7% reported wheeze and 31.6% reported mucus hypersecretion. Smokers were more likely to report these symptoms. Two hundred and ten of the 251 (84%) individuals approached had spirometry and vWF assessed. Eleven percent of these had both an FEV1 < 75% predicted and a forced expiratory ratio (FEV1 forced vital capacity (FVC)) < 70%. Sub-normal spirometry was associated with wheeze, mucus hypersecretion, cigarette smoking and increasing age. By 1996, 32 (15%) of the original group of 210 individuals had died, and 117 of the remaining 178 (66%) had spirometry repeated. FEV1 < 75% predicted was a strong predictor of interim mortality, independent of age, sex and smoking history. The average decline in FEV1 was 46.7 ml yr-1. There was no significant correlation between serum vWF levels and subsequent decline in FEV1. Chronic respiratory symptoms and spirometric evidence of airflow limitation are common in inner-city residents of the U.K., and are associated with smoking history. Much of this disease is unrecognised by health professionals. An FEV1 < 75% predicted is a strong independent predictor of subsequent mortality. The measurement of serum vWF levels is unhelpful in identifying those individuals at increased risk of accelerated decline in FEV1.