Second international collaborative study evaluating performance characteristics of methods measuring the von Willebrand factor cleaving protease (ADAMTS-13)

BACKGROUND: Over the last 4 years ADAMTS-13 measurement underwent dramatic progress with newer and simpler methods. AIMS: Blind evaluation of newer methods for their performance characteristics. DESIGN: The literature was searched for new methods and the authors invited to join the evaluation. Participants were provided with a set of 60 coded frozen plasmas that were prepared centrally by dilutions of one ADAMTS-13-deficient plasma (arbitrarily set at 0%) into one normal-pooled plasma (set at 100%). There were six different test plasmas ranging from 100% to 0%. Each plasma was tested 'blind' 10 times by each method and results expressed as percentage vs. the local and the common standard provided by the organizer. RESULTS: There were eight functional and three antigen assays. Linearity of observed-vs.-expected ADAMTS-13 levels assessed as r2 ranged from 0.931 to 0.998. Between-run reproducibility expressed as the (mean) CV for repeated measurements was below 10% for three methods, 10-15% for five methods and up to 20% for the remaining three. F-values (analysis of variance) calculated to assess the capacity to distinguish between ADAMTS-13 levels (the higher the F-value, the better the capacity) ranged from 3965 to 137. Between-method variability (CV) amounted to 24.8% when calculated vs. the local and to 20.5% when calculated vs. the common standard. Comparative analysis showed that functional assays employing modified von Willebrand factor peptides as substrate for ADAMTS-13 offer the best performance characteristics. CONCLUSIONS: New assays for ADAMTS-13 have the potential to make the investigation/management of patients with thrombotic microangiopathies much easier than in the past.

Ambulatory arterial stiffness index is increased in hypertensive childhood disease

Arterial hypertension in adults is often associated with an increased arterial stiffness, which correlates with the ambulatory arterial stiffness index (AASI) as derived from ambulatory blood pressure (BP) measurements. The purpose of this study was to demonstrate whether children with diagnosed hypertension have an increased AASI as in hypertensive adults. AASI was calculated from 185 ambulatory BP measurements of 114 hypertensive and 71 normotensive, healthy children. Hypertensive children had higher AASI values compared with their normotensive healthy counterparts (0.370 +/- 0.120 versus 0.204 +/- 0.199, p < 0.0001). Children with longer duration of hypertension or a history of primary or secondary aortic coarctation displayed even more elevated AASI values. A receiver operator curve derived cut-off of AASI set at 0.301 distinguished (p < 0.0001) hypertensive from normotensive children with an odds ratio of 8.2, a sensitivity of 81%, and a specificity of 65%. Moreover, AASI correlated with pulse and systolic BP. In conclusion, AASI is elevated in hypertensive children and correlates with the duration and the origin of hypertension in childhood.

Circulating fibrinogen but not D-dimer level is associated with vital exhaustion in school teachers

Meta-analyses have established elevated fibrinogen and D-dimer levels in the circulation as biological risk factors for the development and progression of coronary artery disease (CAD). Here, we investigated whether vital exhaustion (VE), a known psychosocial risk factor for CAD, is associated with fibrinogen and D-dimer levels in a sample of apparently healthy school teachers. The teaching profession has been proposed as a potentially high stressful occupation due to enhanced psychosocial stress at the workplace. Plasma fibrinogen and D-dimer levels were measured in 150 middle-aged male and female teachers derived from the first year of the Trier-Teacher-Stress-Study. Log-transformed levels were analyzed using linear regression. Results yielded a significant association between VE and fibrinogen (p = 0.02) but not D-dimer controlling for relevant covariates. Further investigation of possible interaction effects resulted in a significant association between fibrinogen and the interaction term "VE x gender" (p = 0.05). In a secondary analysis, we reran linear regression models for males and females separately. Gender-specific results revealed that the association between fibrinogen and VE remained significant in males but not females. In sum, the present data support the notion that fibrinogen levels are positively related to VE. Elevated fibrinogen might be one biological pathway by which chronic work stress may impact on teachers' cardiovascular health in the long run.

Heart rate recovery after exercise in chronic heart failure: Role of vital exhaustion and type D personality

OBJECTIVE: Vital exhaustion and type D personality previously predicted mortality and cardiac events in patients with chronic heart failure (CHF). Reduced heart rate recovery (HRR) also predicts morbidity and mortality in CHF. We hypothesized that elevated levels of vital exhaustion and type D personality are both associated with decreased HRR. METHODS: Fifty-one patients with CHF (mean age 58+/-12 years, 82% men) and left ventricular ejection fraction (LVEF) derwent standard exercise testing before receiving outpatient cardiac rehabilitation. They completed the 9-item short form of the Maastricht Vital Exhaustion Questionnaire and the 14-item type D questionnaire asking about negative affectivity and social inhibition. HRR was calculated as the difference between heart rate at the end of exercise and 1min after abrupt cessation of exercise (HRR-1). Regression analyses were adjusted for gender, age, LVEF, and maximum exercise capacity. RESULTS: Vital exhaustion explained 8.4% of the variance in continuous HRR-1 (p=0.045). For each point increase on the vital exhaustion score (range 0-18) there was a mean+/-SEM decrease of 0.54+/-0.26bpm in HRR-1. Type D personality showed a trend toward statistical significance for being associated with lower levels of HRR-1 explaining 6.5% of the variance (p<0.08). The likelihood of having HRR-1D personality than in those without (odds ratio=7.62, 95% CI 1.50-38.80). CONCLUSIONS: Elevated levels of vital exhaustion and type D personality were both independently associated with reduced HRR-1. The findings provide a hitherto not explored psychobiological explanation for poor cardiac outcome in patients with CHF.

Verhalten der Gewichtsdifferenz von selektiv wachstumsretardierten, monochorialen Zwillingen

Problemstellung: Monochoriale Zwillinge (MZ) machen nur ca. 1/3 aller Mehrlinge aus. Im Vergleich zu dichorialen weisen sie jedoch eine höhere Morbidität und Mortalität auf bedingt durch das Transfusionssyndrom, mehr Fehlbildungen und Frühgeburten. In letzter Zeit kristallisiert sich eine weitere Entität heraus, die selektive intrauterine Wachstumsretardierung (sIUWR). Ziel der Studie war es, das Verhalten dieses diskordanten Wachstums im Verlaufe der Schwangerschaft zu untersuchen. Patienten und Methode: Die Diagnose einer monochorialen Situation basiert auf der Darstellung nur einer Plazenta, dem T-Sign sowie gleichgeschlechtiger Feten. Es wurden nur biamniote MZ eingeschlossen. Von einer sIUWR spricht man, wenn folgende Kriterien erfüllt sind: 1) ein Fetus wachstumsretardiert (Abdomenumfang <5. Perzentile) und 2) Gewichtsdifferenz beider Feten >20%. Letztere berechnet sich aus der Differenz der geschätzten fetalen Gewichte dividiert durch das Gewicht des Größeren in% (Delta%). Es wurden die Delta%-Werte bei Diagnosestellung und die letzten Werte vor Geburt verglichen. Ergebnisse: Retrospektiv wurden 23 Fälle mit sIUWR eingeschlossen, davon wurden 13 Fälle longitudinal beurteilt. Das mediane Gestationsalter bei Geburt lag bei 31,4 (16,7–38,6) Wochen. Die Frühgeburtsrate betrug 85,7%, die perinatale Mortalität 11,9%. Der initiale Delta%-Wert lag bei 28±10% und stieg signifikant auf 36,4±9,9%. In allen Fällen nahm der Delta%-Wert zu. Von den Co-Zwillingen waren postnatal 20% auch small for gestational age. Schlussfolgerungen: Bei MZ mit sIUWR ist nach unseren Erfahrungen damit zu rechnen, dass die Gewichtsdifferenz mit zunehmendem Gestationsalter steigt. Diese Zunahme erklärt sich durch eine progressive Verlangsamung der Wachstumsgeschwindigkeit des kleineren Feten. Leider lässt sich anhand der kleinen Fallzahl nicht eruieren, ob dieser D%-Wert und der Grad des Anstieges eine prognostische Bedeutung aufweist.