Combination of EMA-binding and AGLT tests shows the highest diagnostic power for hereditary spherocytosis

Hereditary spherocytosis (HS) is the most common congenital haemolytic anaemia in caucasians

January 24th 2012

Hereditary spherocytosis (HS) is the most common congenital haemolytic anaemia in Caucasians, affecting approximately 1 in 1.000-2.000 individuals. In this disease, as in many other rare diseases, one of the challenges is developing a reliable diagnostic tool. The team from the Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico (Milan), led by Prof. Alberto Zanella, has undergone a performance comparison of several tests to determine which of them is the most useful diagnostic method.

The traditional laboratory diagnosis of hereditary spherocytosis commonly relies on NaCl-based or glycerol-based red cell osmotic fragility tests. More recently, a flow cytometric analysis directly targeting the hereditary spherocytosis molecular defect (EMA-binding test) has been proposed. To determine which one is the better test, the investigators compared the performances of EMA-binding, NaCl-osmotic fragility on fresh and incubated blood, glycerol lysis test, acidified glycerol lysis test (AGLT), and Pink test. Those diagnostic strategies were tested on a series of 150 patients with hereditary spherocytosis, grouped according to the clinical phenotype and the defective protein.

Unfortunately, none of the available tests is able to identify all hereditary spherocytosis cases. EMA-binding displayed 93% sensitivity and 98% specificity. A comparable sensitivity was shown by AGLT (95%) and Pink test (91%). The sensitivity of NaCl osmotic fragility tests, commonly considered the gold standard for diagnosis of hereditary spherocytosis, was 68% on fresh and 81% on incubated blood, and further decreased in compensated cases (53% and 64%). The results of the study were recently published by the scientific magazine Haematologica, with Dr. Paola Bianchi as the first author and the ENERCA member Prof. Alberto Zanella as the last one.

The combination of EMA-binding, that directly targets the structural defect of hereditary spherocytosis, and AGLT, which exploit the red cell surface area to volume ratio, enabled to identify the totality of patients. Thus, this is the combination of tests associated with the highest diagnostic power, even in the mildest or compensated cases. In addition, EMA-binding test shows the greater disease specificity. Since flow cytometer is not available in all diagnostic laboratories, it is worth mentioning that AGLT plus incubated NaCl OF raises the sensitivity to 97%, similarly to what previously reported in a greater series of patients.

Related information

Copyright © 2002 - 2020 Enerca

Co-funded by the Health Programme of the European Union.