Methemalbumin is an albumin

Albumin

Albumin refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat denaturation. They are commonly found in blood plasma, and are unique to other blood proteins in that they are not glycosylated...

 complex consisting of albumin and heme.

This complex gives brown color to plasma

Blood plasma

Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

 and occurs in hemolytic and hemorrhagic disorders.

Its presence in plasma is used to differentiate between hemorrhagic and edematous pancreatitis

Pancreatitis

Pancreatitis is inflammation of the pancreas. It occurs when pancreatic enzymes that digest food are activated in the pancreas instead of the small intestine. It may be acute – beginning suddenly and lasting a few days, or chronic – occurring over many years...

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The Schumm test

Schumm test

The Schumm test is a blood test that uses spectroscopy to determine significant levels of methemalbumin in the blood. A positive result could indicate intravascular hemolysis...

 is used to differentiate intravascular haemolysis from extravascular haemolysis, as in haemolytic anaemias. A positive result is indicative of intravascular haemolysis.