METHODS: Tests for LA include dilute Russell's viper venom time (dRVVT) and Kaolin clotting time (KCT). Patients with LA ratio (dRVVT screen ratio/dRVVT confirm ratio) of ≥1.2 were considered as LA positive irrespective of KCT results. KCT was considered positive if there was a prolongation in KCT screening test which was not corrected on mixing with normal plasma.
RESULTS: Of 577 patients' results, 295 were normal, 178 were KCT positive with negative dRVVT and 104 were LA positive. Incidences of thrombosis, connective tissue disease (CTD) and bad obstetric events were noted in 13%, 16% and 44% of normal patients, 9%, 22% and 49% of KCT+ patients and 23%, 37% and 17% of LA+ patients respectively. On further evaluation of dRVVT screen ratios, 431 had a ratio of <1.1, 59 had a ratio between 1.1 and 1.2 and 87 had a ratio of >1.2. Positive LA results were found in 3%, 29% and 87% of patients with dRVVT screen ratios of <1.1, 1.1 - 1.2 and >1.2 respectively.
CONCLUSION: LA+ patients had higher incidences of thrombosis and CTD as compared to normal and KCT only positive patients. There was no significant difference in clinical characteristics between normal and KCT+ patients which suggests the presence of a high rate of false-positive KCT results. Since confirmatory testing for KCT is not widely used, the option of using another LA screening test method should be considered. In regard to dRVVT testing, confirmatory test should only be performed in patients with prolonged dRVVT screening result which was not corrected upon mixing with normal plasma as required by the International Society of Thrombosis and Haemostasis guidelines on LA testing. This practice will not only result in significant cost reduction but also avoid diagnostic confusion.
CASE REPORT: Her peripheral smear and bone marrow aspirate showed many myeloblasts. Chromosomal study revealed t(8;22;21)(q22;q12;q22) and loss of X chromosome. Fluorescence in situ hybridization (FISH) using whole chromosome painting probes confirmed the three-way translocation involving chromosomes 8, 21 and 22. RUNX1-RUNX1T1 rearrangement was identified in FISH and reverse transcriptase polymerase chain reaction confirming the diagnosis of AML with variant t(8;21). The patient was treated with standard chemotherapy. She achieved morphological remission one month after induction chemotherapy.
DISCUSSION: Although the clinical significance of variant t(8;21) is not well delineated, the evaluation of 31 such cases suggests patients with variant t(8;21) have similar prognosis to those with classical t(8;21).
METHODS: Haemoglobin variants were identified by HbA1c analysis in 93 of 3522 samples sent to our laboratory in a period of 1 month. Haemoglobin analysis identified HbE trait in 81 of 93 samples. To determine the influence of HbE trait on HbA1c analysis by Variant II Tubo 2.0, boronate affinity high performance liquid chromatography (HPLC) method (Primus PDQ) was used as the comparison method. Two stage linear regression analysis, Bland Altman plot and Deming regression analysis were performed to analyse whether the presence of HbE trait produced a statistically significant difference in the results. The total allowable error for HbA1c by the Royal Australasian College of Pathologists (RCPA) external quality assurance is 5%. Hence clinically significant difference is more than 5% at the medical decision level of 6% and 9%.
RESULTS: Statistically and clinically significant higher results were observed in Variant II Turbo 2.0 due to the presence of HbE trait. A positive bias of ∼10% was observed at the medical decision levels.
CONCLUSION: Laboratories should be cautious when evaluating HbA1c results in the presence of haemoglobin variants.