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Table 1 Code Definition of influenza-related complications for all patients

From: Pneumonia and influenza, and respiratory and circulatory hospital admissions in Belgium: a retrospective database study

Influenza-related complications for all patients

ICD-9 codes

Asthma

493, V17.5

Cardiovascular disease

989.1, 402.01, 402.11, 402.91, 404.01, 404.03, 404.11, 404.13, 404.91, 404.93, 428, 413, 412, 410, 411, 414

Chronic obstructive pulmonary disorder

490, 491, 492, 496

Diabetes

250.xx, 249.xx, V18.0, V77.1, 253.5, 588.1

Hypertension

401-405, 997.91, 459.3x (except codes of the 402 and 404 chapters, already listed under cardiovascular disease)

Pneumococcal pneumonia

481

Secondary respiratory infection

480, 482, 483, 484, 485, 486, 460, 462, 466, 390, 391, 392, 041, 465.9, 034.0, 038.0, 320.2, 482.31

Stroke

430-438, 342

  1. Source: International Classification of Disease – 9th Edition; Codes were selected after a review of the literature [915].