Celiac Disease and Unexplained Iron Deficiency in a Primary Care Setting

The primary purpose of the study is to document unexplained iron deficiency and its relationship to celiac disease, iron malabsorption and occult intestinal blood loss. Test results given to primary care physicians may prompt further testing for celiac disease (duodenal biopsy) or other potential causes of occult iron deficiency. The specific endpoints to be evaluated include: * Prevalence of specific serum markers of celiac disease in those with unexplained serum markers of iron deficiency. * Prevalence of iron malabsorption with and without celiac disease in the same population * Frequency of other blood tests for malabsorption and their association with celiac disease or other cause of iron malabsorption. * Frequency of specific historical markers associated with celiac disease * Prevalence of unrecognized GI blood loss * Quality of life improvement based on new diagnoses with appropriate therapy * After one year follow-up, review patient records for additional diagnoses explaining iron deficiency. Primary Objective: Discover several etiologies of unexplained iron deficiency in a primary care clinic population including celiac disease, iron malabsorption and occult intestinal blood loss. Secondary Objectives: * Define percent of total clinic patient population with one or more markers of iron deficiency on last testing and the subset without an apparent etiology on their problem list ("study group"). * Define percent of patients in the study group that are currently iron deficient at time of study onset, and how many of those are actually anemic. * Define percent of study group patients with iron malabsorption, with or without celiac disease. * Document improved quality of life outcomes for those with new diagnoses and appropriate therapy, including celiac disease given gluten-free diet and iron therapy. * For those patients identified with celiac disease, do statistical analysis of historical and lab parameters that are more highly linked to celiac disease to improve screening parameters. * Document percent of various diagnoses that explain occult iron deficiency as found by primary care providers over the course of a one year follow-up after initial diagnosis. (Providers will be given all testing results related to their patients after the initial screening and at one year.) * Specific cost-effectiveness of this screening procedure may be done in a future study if preliminary results are suggestive of improved outcomes.