Dried blood sample analysis

A non-destructive method of estimating hematocrit (Hct) of whole blood from a dried blood sample prepared from the whole blood, the method comprising:

• a) determining the total amount of hemoglobin derivatives comprising oxyhemoglobin, met-hemoglobin and hemichrome in a dried blood sample,
• wherein the total amount of said hemoglobin derivatives in a dried blood sample is determined by measuring the reflectance, absorbance, or transmittance of the dried blood sample at the quasi-isosbestic point of said hemoglobin derivatives, or
• wherein the total amount of said hemoglobin derivatives in a dried blood sample is determined by calculating the sum of the amounts of each of oxyhemoglobin, met-hemoglobin and hemichrome, wherein the amount of each of oxyhemoglobin, met-hemoglobin and hemichrome is determined by measuring the reflectance, absorbance, or transmittance of the dried blood sample at multiple wavelengths, and comparing the measured spectrum with reference spectra of the respective hemoglobin derivatives;
• and
• b) estimating the hematocrit from the total amount of said hemoglobin derivatives, wherein the hematocrit is estimated using a calibration curve providing a correlation between hematocrit and the total amount of said hemoglobin derivatives in a dried blood sample.