Development of algorithms to identify individuals with Neurofibromatosis type 1 within administrative data and electronic medical records in Ontario, Canada

Table 4 Selected commonly used OHIP outpatient diagnostic billing codes in 71 patients with confirmed NF1 and 28,409 clinical encounters

Codes	Description	Frequency	Percent of codes
999	No diagnosis	9838	34.6
304	Drug dependence/drug addiction	1216	4.3
709 or	Other disorders of skin and subcutaneous tissue	822	2.9
216 or	Dermatofibroma, pigmented nevus
173	Other skin malignancies
787	Anorexia/nausea and vomiting	605	2.1
781	Leg cramps, pain (muscle, joints)	372	1.3
300	Anxiety, depression	347	1.2
192	Malignant tumours of the nervous system outside of brain	278	1.0
349	Other diseases of the central nervous system	266	0.9
401	Essential hypertension	241	0.9
758	Autosomal anomalies, chromosomal anomalies	141	0.5
225	Benign tumours of the nervous system	102	0.4
191	Malignant brain tumours	98	0.3
759	Other congenital anomalies	95	0.3
313	Behaviour disorders of childhood and adolescence	60	0.2
315	Developmental delay	45	0.2

Codes 709, 216 and 173 all represent common skin-related issues in NF1, and therefore were combined for these analyses

ISSN: 1750-1172