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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].