Usefulness of measuring fast valley height rate using high-performance liquid chromatography for variant hemoglobin, Hb A2-Niigata.

We have reported cases of hemoglobin (Hb) A2-Niigata (δ1Val → Ala) with δ chain variant Hb and falsely high HbA1c levels. In subjects with Hb A2-Niigata, shoulder-shaped anomalous peak was detected immediately before the HbA1c peaks using high-performance liquid chromatography (HPLC; HLC-723 G9). The phenomenon where the valley between peaks of LA1c+ , a fraction containing labile HbA1c, and HbA1c fraction [fast valley (FV)] became shallow owing to the anomalous peak was observed. In this study, we attempted to quantify the height index of the FV. We assumed that the index FV height rate (FVHR) was useful for screening Hb A2-Niigata. Five subjects with Hb A2-Niigata were compared with the control group of 50 subjects without diabetes and 50 with diabetes. Various indices were measured using HPLC chromatograms, and FVHR was calculated based on these indices. FVHR in subjects with Hb A2-Niigata was significantly higher than that in subjects without and with diabetes (all P < 0.001). Furthermore, when the cutoff value of FVHR was set at 23-30%, Hb A2-Niigata could be diagnosed with high sensitivity and specificity (both 100%). Hb A2-Niigata can be screened using FVHR with high sensitivity and specificity. FVHR might be also useful for screening other variant hemoglobins with abnormal HPLC chromatograph.