[Flowcytometric diagnostics of hereditary spherocytosis]. / Flowcytometrisk diagnostik af hereditaer sfaerocytose.

ABSTRACT

INTRODUCTION: The diagnosis of hereditary spherocytosis (HS) is based upon clinical presentation, typical laboratory findings of haemolysis with an increased mean corpuscular haemoglobin concentration (MCHC) combined with a positive osmotic fragility result. The disorder is caused by structural defects in red cell cytoskeletal proteins. The dye eosin-5'-maleimide (EMA) binds to band three of the red cell membrane. The fluorescence intensity of EMA-labelled red cells can be quantified by flowcytometric analysis. Decreased fluorescence is found in patients with HS. We have evaluated this method by comparing flowcytometric analysis of red cells from patients with HS and patients with other haemolytic disorders. MATERIAL AND METHODS: We included 21 patients with HS and 27 patients with other haemolytic disorders. The red cells were incubated and labelled with EMA followed by flowcytometric analysis measuring the mean-fluorescence-intensity expressed as EMA percentage. RESULTS: Based on the overall results, we assess an EMA percentage threshold of 15 or above to indicate HS. We found a sensitivity of 95% and a specificity of 93%. CONCLUSION: The osmotic fragility test does not have the same high degree of sensitivity and specificity and the test is time-consuming in the laboratory setting. Flowcytometric analysis with quantification of fluorescence intensity of red cells labelled with the EMA dye has proven to be a rapid and user-friendly method available to any laboratory with a flowcytometer. The method has a high sensitivity and specificity and can be recommended as a diagnostic tool for HS.