Methylene blue reduction test is essentially an aromatic chemical compound which is useful in determining a type of the blood disorder known as methemoglobinemia. Methemoglobinemia is a condition in which the iron in the hemoglobin molecule is malfunctioning thus making it unable to carry oxygen to the various tissues in an effective manner. Methylene blue at room temperature is solid, odorless and exists in the form of a dark green powder which when dissolved in water forms a blue solution. Sometimes methylene blue is also referred to as methylthioninium chloride.
The methylene blue reduction test is performed by a trained healthcare provider by using a blood pressure cuff, also called a tourniquet. This will be wrapped around your upper arm. This is done to create pressure so that the veins below the elbow will fill up with blood. An antiseptic is then applied to make the area in which a test needle is to be inserted free of any germs. The needle is inserted in the inside of the elbow or at the back of the hand. A catheter, which is a thin tube, is then placed into the vein like an IV. When the tube stays in place the tourniquet is then removed. The dark green powder that is methylthioninium chloride is then introduced into the catheter and this goes into your veins. Observation is then carried out on how the powder turns methemoglobin into normal hemoglobin. It is normal to feel some pain or a stinging sensation when the needle is introduced into the vein, and later on there may be some throbbing.
There are several know causes for the condition referred to as methemoglobinemia, most of them are considered to be genetic. A methylene blue reduction test is useful in differentiating between methemoglobinemia, which is caused due to the presence of the enzyme cytochrome b5 reductase in insufficient proportions and other genetically inherited types of methemoglobinemia. It is normally observed that methylene blue rapidly lowers the methemoglobin level in the blood. However if the methylene blue does not cause the blood level of methemoglobin to reduce, a rare form of methemoglobinemia may be the cause.
There are several minor risks involved when it comes to taking the methylene blue reduction test. Excessive bleeding, feeling lightheaded or even fainting or blood building up under the skin is the most commonly observed risks. In some cases due to the variation in the size of the veins, multiple attempts are required to get the needle in the right place. There also is a slight chance of infection where the skin is broken, however all these are minor risks.