The Alpha haemoglobin-stabilising protein (AHSP) is a key chaperone molecule synthesised in red blood cell (RBC) precursors. In this study, the inventors have developed a sandwich ELISA method which allows the quantification of AHSP protein in RBCs of normal subjects and in sickle cell anaemia (SCA) patients treated or untreated by hydroxycarbamide. AHSP was significantly more abundant in untreated SCA patients than in controls (p< .0001). After hydroxycarbamide treatment, the AHSP decreased but remained significantly more abundant than in controls. A highly positive correlation was found between AHSP concentration and the ?-Hb pool. So, like the ?-Hb pool, the AHSP concentration could be a new and better RBC biomarker of SCA disease, much more easily measurable than the ?-Hb pool. The AHSP ELISA dosage will facilitate the study of AHSP under different pathological conditions and could be a novel method of monitoring the AHSP translation regulation not only in RBCs but also in the different tissues where it is expressed. Thus, the present invention refers to a method for prognosing a haemoglobin-related disorder, such as sickle cell anaemia, in a subject in need thereof comprising measuring the level of AHSP by sandwich Elisa technique.