The present disclosure provides methods for determining
optical absorbance of a blood sample, methods for identifying the presence or absence of sickle haemoglobin in a blood sample, kits and devices thereof The present methods comprise measuring a first
absorbance of the blood sample under a deoxygenated condition at 420-440 nm and measuring a second
absorbance of the blood sample under the deoxygenated condition at 541-570 nm. A ratio of the second
absorbance to the first absorbance and a difference between the first absorbance and the second absorbance are calculated and employed to identify the presence or absence of sickle haemoglobin and determine the amount of sickle haemoglobin. The methods, kits and devices of the present disclosure are simple, low cost, and provide a rapid way to identify the presence or absence of and amount of sickle haemoglobin in a blood sample in a point-of-
care setting.