Resistance to activated protein C in thalassaemic patients: an underlying cause of thrombosis.
We evaluated 81 thalassaemia major and 4 thalassaemia intermedia patients (48 M, 37 F), median age 17 years; 62/85 patients were HCV-positive, 3/85 HIV-positive, 19/85 were splenectomized. Forty normal healthy children were recruited as the control group. The number of thrombotic events was studied retrospectively. Platelet poor plasma was filtered and quick-frozen at -70 degrees C until time of assay. APC resistance was measured in an activated thromboplastin time and results were expressed as normalized ratio. All tests were done with diluted 1 in 5 (v/v) factor V deficient plasma and with undiluted plasma. Molecular genetic investigation of factor V gene was performed with polymerase chain reaction, followed by digestion of amplified products with restriction enzyme Mnl I. Data obtained with molecular investigation revealed the presence of 4 heterozygous subjects for factor V Leiden (4.7%). Functional tests were able to detect all heterozygotes for factor V Leiden both with undiluted and with diluted plasma, and there were no false negative subjects. However, undiluted plasma revealed a greater number of false positive subjects (n=15) than did diluted plasma. Therefore, tests done with undiluted and diluted plasma revealed a 100% sensitivity, while specificity was 81% for undiluted plasma and 97% for diluted plasma. Only one thrombotic event was observed in one of the 85 studied patients, as a case of stroke in a thalassaemia intermedia patient with APC resistance. In the same patient an additional thrombogenic risk factor was represented by a pronounced haematocrit increase at the beginning of her transfusion regimen.
Giordano
P
P
Department of Biomedicine of Developmental Age, University of Bari, Italy.
Del Vecchio
G C
GC
Altomare
M
M
Coppola
B
B
Schettini
F
F
Iolascon
A
A
De Mattia
D
D
D000293:Adolescent; D000328:Adult; D002561:Cerebrovascular Disorders / Q000097:blood / Q000209:etiology / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D005165:Factor V / Q000235:genetics; D005260:Female; D006580:Genetic Carrier Screening; D006801:Humans; D008297:Male; D010314:Partial Thromboplastin Time; D011486:Protein C / Q000378:metabolism*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013789:Thalassemia / Q000097:blood* / Q000150:complications* / Q000235:genetics; D013927:Thrombosis / Q000097:blood / Q000209:etiology* / Q000235:genetics
D011486:Protein C; C095381:factor V Leiden; D005165:Factor V