Hubungan antara rerata kadar feritin dalam serum dengan gejala klinis gangguan pemusatan perhatian dan hiperaktivitas berdasarkan skala penilaian perilaku anak hiperaktif Indonesia (SPPAHI) = Relationship between serum ferritin and clinical symptoms of attention deficit hyperactivity disorder based on skala penilaian perilaku anak hiperaktif Indonesia (SPPAHI)