Platelet function and the von Willebrand factor antigen in the hepatosplenic form of schistosomiasis mansoni

Abstract

Forty-five individuals with hepatosplenic schistosomiasis mansoni were studied with the aim of measuring levels of von Willebrand factor antigen (vWF:Ag), detecting abnormalities in platelet morphology and aggregation, and identifying changes to surface antigens. Haemograms, platelet aggregation tests, flow cytometry investigations of CD41/CD42b antibody and vWF:Ag assays were performed. Mean platelet counts were low (77,522/mm3) and 82.2% of patients presented thrombocytopenia. An inverse relationship between spleen size and platelet count was seen. Macroplatelets were found in 57.1% of patients, indicating good bone-marrow response, but were insufficient to compensate for the decrease in platelets due to splenomegaly. Decreased or absent platelet aggregation was seen in 50% of patients, probably due to low platelet counts. Markers for GPIIb/IIIa were normal in more than 90% of patients, not supporting the increased capture and destruction of platelets in the spleen that is hypothesized to occur with cirrhosis. Similar to cirrhosis, vWF:Ag levels were high or very high in 70.5% of patients. High levels of vWF:Ag were associated with platelet counts <100,000/mm3, larger spleen diameter and oesophageal varices. In conclusion, hepatosplenic schistosomiasis leads to a lower platelet count due to pooling in the spleen and, consequently, impaired aggregation, but not to increased capture and destruction of platelets in the spleen. High vWF:Ag levels probably promote stabilization of platelet microaggregates and prevent minor manifestations of thrombocytopenia such as petechiae, ecchymosis and gingival bleeding.

New index for the diagnosis of liver fibrosis in Schistosomiasis mansoni

“…In schistosomiasis, the changes of the intrahepatic biliary tree, either by ductal injuries caused by ovular reactions or arising from of PPF, could be the anatomical substrate for the increase of this enzyme (3,34) . The platelet count in the blood has been an indicator of severity in schistosomiasis by increasing the risk of bleeding, with its numerical reduction related to the presence of portal hypertension (8,31) and PPF (7) . Some schistosomiasis studies that evaluated platelets and other serum markers have reported lower platelet levels in patients with more advanced fibrosis (2,12,16) .…”

Correlation Between Platelet Count and Both Liver Fibrosis and Spleen Diameter in Patients With Schistosomiasis Mansoni

“…Using ultrasound with the Niamey classification as the gold standard, correlations have been described between patterns of fibrosis and serum levels of IgG and hyaluronic acid (5,22) . Though, the determination of these substances requires sophisticated methods that are generally not available in simpler laboratories found in endemic regions for schistosomiasis.…”

“…Besides the proteins responsible for fibrogenesis others stemming from the degradation process of the extracellular matrix have been studied in the evaluation of fibrosis, such as hyaluronic acid, laminin and type IV collagen (10,16,19,27) . Likewise, the number of platelets is reported to be inversely correlated with the intensity of periportal fibrosis due to the sequestering of platelets in the splenic parenchyma stemming from splenomegaly (5,12,17,23) . Considering the scarcity of accurate data regarding the measurement of fibrosis using serum markers in patients with SM, the aim of this study was to correlate platelet count with both the periportal fibrosis pattern and spleen diameter as evaluated through an ultrasound exam.…”

“…Indeed, a correlation has been described between the intensity of periportal fibrosis and pressure levels in the portal vein, which can lead to bleeding through esophageal varices; moreover, an association has been described between the presence of esophageal varices and spleen diameter (1,21) . Liver biopsy (7) , an ultrasound examination of the abdomen (3,8) , serum markers (5,10,16,22) , platelet count (4,12) and, more recently, liver stiffness (elastography) measurement (9) have been used to assess the fibrosis that develops in chronic liver disease. With SM, the liver-wedge biopsy is the most accurate method for measuring periportal fibrosis, but implies the use of laparotomy.…”

Ultrasound versus biological markers in the evaluation of periportal fibrosis in human Schistosoma mansoni

“…Additionally, an inverse relationship between spleen size and PLT was suggested by Correia et al (2009b).…”