The causes of an isolated prolonged activated partial thromboplastin time (APTT) with a normal prothrombin time (PT) are either a deficiency of clotting factors VIII, IX, XI or XII or the presence of an inhibitor. The inhibitor may be specific to an individual clotting factor or it may be a non-specific inhibitor like the lupus anticoagulant which has opposite therapeutic implications. We report a patient referred to our hospital for treatment that was previously diagnosed at another medical institution as an acquired factor IX inhibitor following an investigation for a prolonged APTT. On further testing this turned out to be a potent lupus anticoagulant which interfered with the phospholipid-dependent factor assays. The use of dilution studies, chromogenic assays and phospholipid neutralization can help differentiate these inhibitors. Great care must be taken in the interpretation of factor assays in the presence of lupus anticoagulant to avoid misdiagnosis and inappropriate treatment.
Thalassaemia is a common disorder in Malaysia. It is estimated that 4.5% of the population are carriers for beta- or alpha- thalassaemias. We set out to screen Form 4 students aged between 15 and 16 years old in a national school, for thalassaemia in March 2008. Written consent was obtained from 310 students. The carrier rate for the common thalassaemia syndromes was 6.8% (2.9% for beta-thalassaemia, 2.6% for HbE and 1.3% for two-gene deletion for alpha-thalassaemia). Carriers for beta-thalassaemia and two-gene deletion for alpha-thalassaemia were more common in the Chinese (4.3% and 1.4% respectively) while heterozygous HbE was more common in the Malays (3.8%). The laboratory cost of screening one student was RM 45 and the total number of man-hours spent in this screening activity was 600. This screening exercise showed that thalassaemia carriers are common among the Chinese and Malays and it is feasible to carry out a screening programme for secondary school students.