Impact of additive solutions on haematocrit measurement and red blood cell integrity: A comparative study of SAGM and PAGGSM.

BACKGROUND AND OBJECTIVES: Accurate haematocrit (Ht) measurement of red cell concentrates (RCCs) is critical because it is used to calculate the level of haemolysis, a key RCC quality control parameter. The hypothesis was that Ht depends on both the measurement method (microcapillary vs. haematology analysers) and the additive solution (hypertonic saline-adenine-glucose-mannitol [SAGM] vs. isotonic phosphate-adenine-glucose-guanosine-saline-mannitol [PAGGSM]). We quantified method- and solution-related effects on Ht measurement and assessed the downstream consequences for haemolysis. Storage-induced micro-erythrocytes (SMEs) were evaluated as a secondary marker of morphological preservation. MATERIALS AND METHODS: RCCs were produced from whole blood (N = 16). Using a pool-and-split design, eight paired RCCs were assigned to SAGM or PAGGSM and stored for 21 days. Ht was measured by HT200 microcapillary and haematology analysers. Red blood cell (RBC) morphology and SMEs were assessed by imaging flow cytometry. RESULTS: At Day 1, microcapillary Ht in PAGGSM exceeded analyser-derived Ht by 3.6%-10%, whereas SAGM Ht was more consistent. Using different Ht sources materially altered haemolysis estimates. Over storage, PAGGSM showed a decline in Ht (65.3%-62.6%) accompanied by reduced RBC projected surface area (73.9-71.01 μm2). SAGM showed stable Ht but reduced RBC projected surface area (72.6-69.1 μm2). SME accumulation was lower in PAGGSM at Day 21 (13.6%) than in SAGM (18.8%). CONCLUSION: Ht measurement method materially impacts haemolysis, underscoring the need to standardize Ht assessment and to prefer microcapillary Ht when calculating haemolysis. Additive solution also influences storage quality: PAGGSM better preserved RBC morphology and reduced SMEs relative to SAGM up to Day 21.