Table 3.

Percentage of Visits by Primary Diagnosis Group

		Percentage of Visits, Weighted
Primary Diagnosis Group	ICD-9-CM Codes	PRINS	NAMCS Mean (95% CI)
Infectious and parasitic diseases	001–139	4.7	3.5 (3.3–3.7)
Neoplasm	140–239	0.8	1.1 (1.0–1.2)
Endocrine, nutritional, metabolic diseases; immunity disorders	240–279	10.2	9.5 (9.0–9.9)
Mental disorders	290–319	5.3	4.2 (4.0–4.4)
Diseases of the nervous system and sense organs	320–389	7.6	6.1 (5.9–6.4)
Diseases of the circulatory system	390–459	9.9	11.9 (11.3–12.6)
Diseases of the respiratory system	460–519	15.8	16.5 (16.0–17.1)
Diseases of the digestive system	520–579	4.0	4.2 (4.0–4.4)
Diseases of the genitourinary system	580–629	3.6	3.6 (3.4–3.8)
Diseases of the skin and subcutaneous tissue	680–709	4.4	3.7 (3.5–3.9)
Diseases of the musculoskeletal and connective tissue	710–739	5.1	8.0 (7.6–8.4)
Symptoms, signs, and ill-defined conditions	780–799	8.0	8.0 (7.7–8.3)
Injury and poisoning	800–999	3.7	4.5 (4.3–4.8)
Supplementary classification	V01–V82	15.3	13.8 (13.1–14.5)
All other diagnoses/unknown	–*	1.7	1.3 (1.2–1.4)

ICD-9-CM = International Classification of Diseases, Ninth Revision, Clinical Modification; PRINS = Primary Care Network Survey; NAMCS = National Ambulatory Medical Care Survey; CI = confidence interval.

* Includes diseases of the blood and organs (280–289); complications of pregnancy, childbirth, and the puerperium (630–677); congenital anomalies (740–759); certain conditions originating in the perinatal period (760–779); and diagnoses that were uncodable (patient left before being seen; patient was transferred to another facility; health maintenance organization did not authorize treatment; entry was “none,” “no diagnosis,” “no disease,” or “healthy”). Unknown includes blank diagnoses, uncodable diagnoses, and illegible diagnoses.