If a thorough history or physical examination does not indicate a particular cause, most experts recommend limiting screening tests to Complete blood count with differential Erythrocyte sedimentation rate Blood urea nitrogen and serum creatinine and electrolyte levels Urinalysis (including ability to concentrate and acidify) and culture Stool for pH, reducing substances, odor, color, consistency, and fat content Depending on prevalence of specific disorders in the community, blood lead level, HIV, or tuberculosis testing may be warranted.