Diagnostic performance of morphological analysis and red blood cell parameter-based algorithms in the routine laboratory screening of heterozygous haemoglobinopathies.

Abstract

Objectives: The aim of this study was to carry out a cross-analysis of the morphological abnormalities (MA) and the electrophoretic profile (EP) of blood samples suspect for heterozygous haemoglobinopathies (HTZ HGP). Screening for HTZ HGP was based on erythrocyte parameters provided by the Sysmex XN analysers.

Methods: A total of 596,000 blood samples was included in the study. According to the results of the mean corpuscular haemoglobin concentration (MCHC), the percentage of microcytes (Micro%) and the standard deviation of the red blood cell distribution width (RDW-SD), 842 different adults were screened as suspect for HTZ HGP and underwent simultaneous morphological analysis of red blood cells (RBCMA) and haemoglobin fraction analysis.

Results: The majority (72.8 %) of HTZ HGP suspects presented a pathological EP, mostly compatible with a confirmed β-thalassaemia trait (50.1 %) or a heterozygous β-haemoglobin variant (12.2 %). MA were identified in 360 (42.8 %) samples and 70 (8.3 %) of these had 3 or more MA. The most common MA was poikilocytosis (28.1 %). Patients with at least 1 MA detected were more likely to have a pathological EP (p=0.003). However, correlation between the number of MA detected and the type of EP was negligible.

Conclusions: Screening for HTZ HGP based on erythrocyte parameters measured on Sysmex XN analysers is a relevant tool with a positive predictive value of 72.8 % and definitely superior to microscopic RBCMA which now appears to be of low added value and obsolete in this indication.