Table 1.

Levels of evidence for the diagnosis of ITP established by medical record review

Evidence level	Description
Definite ITP	1. A hematologist records the diagnosis of ITP 2. A non-hematologist records the diagnosis of ITP (with no record that a hematologist was consulted) and documents the patient was currently being followed for ITP
Probable ITP	1. A hematologist describes “thrombocytopenia” or “low platelet count” in a child without specifically stating the diagnosis of ITP 2. A non-hematologist records the diagnosis of ITP but does not document the patient was currently being followed for ITP 3. A non-hematologist describes “thrombocytopenia” or “low platelet count” without specifically stating the diagnosis of ITP
Unlikely ITP	1. A hematologist describes “thrombocytopenia” or “low platelet count” in an adult without specifically stating the diagnosis of ITP 2. A non-hematologist records the diagnosis of ITP but within one year a different physician (hematologist or non-hematologist) states that the thrombocytopenia is due to a different etiology (e.g., chemotherapy, HIV infection)
Not ITP, correct code	The patient has another disease for which the ICD-9-CM code of 287.3 is correct
Not ITP, incorrect code	The hematologist or non-hematologist records the diagnosis of a disease that should not have been coded as 287.3 or states that the thrombocytopenia is due to another condition (e.g., chemotherapy, HIV infection), excluding the diagnosis of ITP