Background:The osmotic fragility (OF) test is one of the most suitable procedures to determine the resistance of the erythrocyte membrane under conditions of osmotic stress. One of the most frequent clinical uses of the FO test is the diagnosis of hereditary conditions that affect erythrocytes: thalassemia and spherocytosis. Both conditions induce red blood cells (RBCs) to be prone to swelling and then lyse under osmotic stress faster than those RBCs without any pathology. Since the standard OF test is time consuming and needs specialized equipment, a fast, accessible, and reliable technique is necessary to determine the OF. Objective: The objective of the study was to evaluate an alternative technique to determine the OF of erythrocytes by refractive index (RI) measurements. The method consists of measuring the real part of the RI of dilutions of whole blood samples with hypotonic solutions at different NaCl concentrations, ranging from 0% to 0.9% using a standard Abbe refractometer. Materials and methods: An experimental study was carried out with volunteers who went to the General Hospital of Mexico "Eduardo Liceaga. " Peripheral blood samples from 12 healthy volunteers were used through the standard blood draw procedure and stored in a heparinized vacutainer tube. Results and conclusions: The proposed technique that uses an Abbe refractometer to measure the infrared of different solutions of whole blood and hypotonic solutions to determine the OF curve has proven to be simpler and more robust than the standard method based on the measurement of light absorption in dilutions of hemolyzed blood. The determination of the OF of erythrocytes rapidly and straightforwardly can be useful in the detection of specific pathologies.

Today, visual classification of the degree of lipemia in blood samples is frequently performed in clinical laboratories. However, achieving standardization of this classification at low cost and with fewer resources is an objective that is still under development. In this work, a comparison is made between the visual inspection and optical measurements of blood plasma for quantifying lipemia. The plasma refractive index’s real part was measured using an Abbe refractometer and transmittance measurements were made at a 589 nm wavelength and wavelengths ranging from 320 to 1100 nm in the spectral region, respectively. Taking the slope of the transmittance spectrum at two specific wavelengths, it is possible to establish a more standardized selection criterion and implement it quickly using low-cost optical devices. Furthermore, using the proposed transmittance-spectrum-slope method, statistically significant differences (p < 0.05) were found between healthy blood samples and lipemia 1, 2, 3, and 4. However, there were no statistical differences between lipemia 1 and 2.