Influencia de las variables preanalíticas en la determinación de proteína S / Influence of preanalytical variables in S protein determination

La proteína S (PS) regula el sistema de coagulación mostrando actividad de cofactor de la Proteína C activada (PCa) con la cual forma un complejo equimolecular. En presencia de iones calcio este complejo inactiva por proteólisis los factores V y VIII activados por trombina. La proteína S plasmática circula 40% libre (fracción que presenta actividad de cofactor de la PCa) y 60% unida al C4-BP (proteína ligante de la fracción C4 del complemento). El objetivo fue comparar el dosaje de PS realizado por método coagulable e inmunoturbidimétrico e investigar cómo las variables preanalíticas afectan los niveles de PS determinados. Se obtuvieron los siguientes resultados: método coagulable: CV intra ensayo: (n=20): 4%, CV interensayo (n=20, 3 días): 3,4%. Método inmunoturbidimétrico: CV intraensayo (n=20): 3,7%.CV Inter. ensayo (n=20,3 días): 4,5%. Existe buena correlación (R2=0,94) entre ambos métodos, cuando la calibración por el método coagulable se realiza en la misma corrida analítica que las muestras. Cuando se realizó el estudio de Bland y Altman los dos métodos mostraron ser comparables en todos los niveles de PS estudiados. No se observaron diferencias significativas entre las muestras determinadas frescas y conservadas a -20 y -80 °C descongeladas solo una vez.

Protein S has an essential anticoagulant function acting as activated Protein C cofactor and forming an equimolecular complex with it. In the presence of calcium this complex regulates the coagulation process inactivating thrombin activated factors V and VIII by proteolysis. In plasma there are two different forms: a) free Protein S which acts as the cofactor of activated protein C (representing about 40% of total Protein S) and b) C4-BP(C4 binding protein) bound protein S which exhibits no activity as cofactor of activated Protein C (representing about 60% of total PS). The objetive was to compare the PS dosage determination by two methods: immunoturbidimetric and clotting, and to investigate how pre-analytical variables affect the results. The following results were obtained: Clotting method: CV intra assay: (n=20): 4%, CV interassay (n=20, 3 days): 3.4%; immunoturbidimetric method CV intra assay (n=20): 3.7%: CV inter assay (n=20.3 days): 4.5%. There is a good correlation (R2 = 0.94) between both methods; when the clotting method is calibrated in batch with the samples. There is significant difference between fresh and frozen ( -20 °C and -80 °C) samples when the latter have been desfrozen only once.

Cerebral Infarction Associated with Free Protein S Deficiency

BACKGROUND: Coagulation abnormalities account for 1% to 5% of the causes of adult stroke. The importance of pro-thrombotic condition as a cause of stroke has been the subject of intense controversy. The role of protein S deficiency in the etiology of stroke and the clinical pattern of cerebral infarction caused by the prothrombotic state are still unclear. We investigated clinical characteristics of cerebral infarction caused by free protein S (FPS) deficiency. METHODS: We enrolled patients with cerebral infarction over 2 years. Cerebral infarction was classified into transient ischemic attack, lacunar infarction, embolic infarction, and thrombotic infarction. We assayed free protein S, prothrom-bin time (PT), and activated partial thromboplastin time (APTT) within 24 hours after stroke and measured free protein S and protein S Ag at 3 months after cerebral infarction. All patients underwent a cardiological examination and neu-roimaging study, and cerebral angiography was done only when necessary. RESULTS: Eight patients (1.67%) among 474 patients with cerebral infarction had FPS deficiency as a cause of stroke. Four were male and four were female. The history of venous thrombosis was not noted. The age of patients were from 24 to 83 years old at the time of stroke. Two patients had family members with FPS deficiency. The types of stroke were variable, such as thrombotic infarction in 3 patients, lacunar infarction in 4 patients, and embolic infarction in one patient. Cerebral arterial stenosis was noted in 3 patients. Other associated risk factors of stroke were smoking, hypertension, pregnancy, low HDL cholesterol, sinus bradycardia, left ventricular hypertrophy on EKG, and old age. All patients had normal PT, APTT, and liver function test. CONCLUSIONS: FPS deficiency can be a risk factor for cerebral infarction in young patients as well as old patients. Free protein S (FPS) deficiency may increase risk of cerebral infarction in the presence of other risk factors of stroke but this requires confirmation by a large study in unselected patients.

Cerebral Venous Sinus Thrombosis Associated with Antithrombin III Deficiency: A Case Report

Antithrombin III deficient individuals have an increased risk of venous thrombosis and thromboembolism at a young age. To our knowledge, cerebral venous thrombosis associated with antithrombin III deficiency has not yet been reported in Korea. A 27-year-old pregnant woman without any known stroke risk factors was admitted to our hospital because of convulsions. Brain MRI and MR venography showed dural sinus thrombosis of the superior sagittal sinus, straight sinus, and left lateral sinus with venous hemorrhagic infarctions in both frontal and parietal lobes. Antithrombin III concentrations were decreased to 37%. We speculated that the etiology of the cerebral venous thrombosis in this patient was associated with antithrombin III deficiency. We suggest that antithrombin III deficiency should be considered as a possible cause of cerebral venous thrombosis.