related virus) testing rather than HIV testing. In the same study, >90% of HTLV tests were ordered erroneously. It is estimated that between 10 and 15% of physician diagnoses are erroneous. Misdiagnosis of lower extremity cellulitis is estimated to occur in 30% of patients, leading to unnecessary hospitalizations in 85% and unnecessary antibiotic use in 92%. Collectively, these errors lead to between 50,000 and 130,000 unnecessary hospitalizations and between $195 and $515 million in avoidable health care spending annually in the United States. Misdiagnosis of psychological disorders Female sexual desire sometimes used to be diagnosed as female hysteria. Sensitivities to foods and food allergies risk being misdiagnosed as the anxiety disorder orthorexia. Studies have found that bipolar disorder has often been misdiagnosed as major depression. Its early diagnosis necessitates that clinicians pay attention to the features of the patient's depression and also look for present or prior hypomanic or manic symptomatology. The misdiagnosis of schizophrenia is also a common problem. There may be long delays of patients getting a correct diagnosis of this disorder. Delayed sleep phase disorder is often confused with: psychophysiological insomnia; depression; psychiatric disorders such as schizophrenia, ADHD or ADD; other sleep disorders; or school refusal. Practitioners of sleep medicine point out the dismally low rate of accurate diagnosis of the disorder, and have often asked for better physician education on sleep disorders. Cluster headaches are often misdiagnosed, mismanaged, or undiagnosed for many years; they may be confused with migraine, "cluster-like" headache (or mimics), CH subtypes, other TACs ( trigeminal autonomic cephalalgias), or other types of primary or secondary headache syndrome. Cluster-like head pain may be diagnosed as secondary headache rather than cluster headache. Under-recognition of CH by health care professionals is reflected in consistent findings in Europe and the United States that the average time to diagnosis is around seven years. Asperger syndrome and autism tend to get undiagnosed or delayed recognition and delayed diagnosis or misdiagnosed. Delayed or mistaken diagnosis can be traumatic for individuals and families; for example, misdiagnosis can lead to medications that worsen behavior. The DSM-5 field trials included "test-retest reliability" which involved different clinicians doing independent evaluations of the same patient—a new approach to the study of diagnostic reliability. Outpatient vs. inpatient Misdiagnosis is the leading cause of medical error in outpatient facilities. Since the National Institute of Medicine's 1999 report, "To Err is Human," found up to 98,000 hospital patients