Division of Nephrology, Department of Medicine, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan. Sugi Hospital, Omuta, Fukuoka 837-0916, Japan. Wada Cardiovascular Clinic, Tosu, Saga 841-0071, Japan. Kurume Ekimae Clinic, Kurume, Fukuoka 830-0023, Japan. Shin Koga Clinic, Kurume, Fukuoka 830-0033, Japan. Koga 21 Hospital, Kurume, Fukuoka 839-0801, Japan. Research Institute of Medical Mass Spectrometry, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan.