Experimental Factor Ontology id EFO_0009226 (Methemoglobin to Total Hemoglobin Ratio Measurement) is the determination of the ratio of methemoglobin compared to total hemoglobin present in a sample. The measurement may be expressed as a ratio or percentage. [ NCI ]. Also known as: HGBMHGB, Methemoglobin/Total Hemoglobin.