Hemoglobin and zinc protoporphyrin (ZPP) tests are commonly used to screen for iron deficiency, but little research has been done to systematically evaluate the sensitivity and specificity of these two tests. The goal of this study was to evaluate the effectiveness of zinc protoporphyrin/heme (ZPP/H) ratio as a point-of-service screening test for iron deficiency among preschool-aged children by comparing the sensitivity and specificity of hemoglobin, ZPP/H ratio, and serum ferritin (SF). Also completed were assessments for the prevalence of anemia, iron deficiency (ID), and iron deficiency anemia (IDA) with indicators of ferritin models. This study was carried out with 95 children ages 3 to 6 y. Anthropometric measurements were assessed and blood samples were analyzed for hemoglobin, SF, transferrin saturation (TS), and ZPP. Anemia was common and the prevalences of anemia, ID, and IDA were 14.7%, 12.6%, and 5.2%, respectively. The ZPP/H ratio was strongly and significantly correlated with hemoglobin. And ZPP/H ratio was a more sensitive test for ID than hemoglobin or SF measurement, correctly identifying more than twice as many iron-deficient children (sensitivity of 91.7%, compared to 41.7% for hemoglobin and SF). However, ZPP/H ratio had lower specificity (60.2%, compared to 89.1% for hemoglobin or 96.4% for SF) and resulted in the false identification of more subjects who actually were not iron deficient than did hemoglobin or SF. Low hemoglobin concentration is a late-stage indicator of ID, but ZPP/H ratio can detect ID at early stages and can be performed easily at a relatively low cost. Therefore, ZPP/H ratio can serve as a potential screening test for pre-anemic iron deficiency in community pediatric practices.