Avaliação da função respiratória: comparação entre valores de referência percentuais fixos e o 5º percentil para diagnóstico de obstrução das vias aéreas
Lung function evaluation: comparing fixed percentage reference values vs. the 5th percentile in the diagnosis of airway obstruction
Luís Miguel Borrego; Mariana Couto; Isabel Almeida; Lara Pimenta; Sara Matos; Mário Morais-Almeida
Resumo
Introdução: Têm sido utilizados critérios fixos para avaliação funcional de doentes com patologia respiratória. É atualmente recomendado pelas orientações internacionais a utilização preferencial do limite inferior do normal (LIN) e limite superior do normal (LSN) (inferior ou superior ao 5º percentil). Objetivo: Comparar os resultados das provas de função respiratória (PFR), utilizando os valores percentuais fixos versus 5º percentil (método de referência), como limites da normalidade, no diagnóstico funcional de obstrução das vias aéreas. Métodos: Análise retrospetiva dos registos de PFR (espirometria e pletismografia corporal) efetuados pelos autores em 2011. Foi avaliada a concordância entre os dois métodos na amostra global, sendo os doentes distribuídos por faixas etárias. Posteriormente foram selecionadas as PFR com razão VEF1/CV < LIN. Nestas, foram analisados os parâmetros VEF1, CVF, CPT e VR quando considerados o 5º percentil versus valores percentuais fixos. A análise estatística for realizada utilizando-se o kappa de Cohen. Resultados: Em 2011, 1.358 indivíduos realizaram PFR. Foram excluídos 8 por dados incompletos. De forma geral, o grau de concordância entre os dois critérios foi bom (valor de Kappa = 0,655±0,035). Entretanto, entre os 124 doentes que apresentavam obstrução pelo LIN, 32 (26%) tiveram um teste normal pelo cut-off de 0,70, pelo que seriam erroneamente subdiagnosticados. Este fato foi verificado apenas nas faixas etárias mais jovens, enquanto nos grupos etários mais idosos se observou uma elevada taxa de sobrediagnóstico (51 indivíduos, 36%). Entre os doentes com obstrução, a concordância para os restantes parâmetros foi boa, exceto para a hiperinsuflação diagnosticada por CPT. Conclusão: A utilização de valores percentuais fixos para diagnóstico de obstrução resulta em elevada taxa de subdiagnóstico em idades jovens e sobrediagnóstico em idade avançadas.
Palavras-chave
Abstract
Introduction: Fixed criteria have been traditionally used in the functional characterization of patients with respiratory disease. International guidelines currently recommend the preferential use of the lower limit of normal (LLN) and the upper limit of normal (ULN) (below or above the 5th percentile). Objective: To compare the results of lung function (LF) tests obtained in clinical practice for the diagnosis of airway obstruction using fixed percentage values vs. the 5th percentile (reference standard) as normality limit. Methods: LF tests (spirometry and body plethysmography) performed in 2011 by the authors were retrospectively analyzed. Concordance between both methods in the global sample was evaluated, and data were analyzed according to age group. Patients meeting criteria for airway obstruction (FEV1/VC ratio < LLN) were selected and had the following variables analyzed considering the 5th percentile vs. fixed percentage values: FEV1/VC, FEV1, FVC, TLC, and RV. Statistical analysis was performed using Cohen’s kappa. Results: Over the year 2011, 1,358 subjects underwent LF tests; eight were excluded due to incomplete data. Overall, the concordance rate between the two criteria was good (kappa value = 0.655±0.035). However, of the 124 patients diagnosed with obstruction using the LLN, 32 (26%) showed a normal test using the 0.70 cut-off, and would therefore be underdiagnosed. These results were found only in younger age groups, while in older patients a high rate of overdiagnosis was observed (51 subjects, 36%). Among patients diagnosed with airway obstruction, concordance between the two criteria was good for the remaining parameters, except for hyperinflation diagnosed with TLC. Conclusion: The use of fixed percentage values in the diagnosis of airway obstruction leads to a high rate of underdiagnosis in younger patients and overdiagnosis in older ones.
Keywords
Referências
1. Miller MR, Pincock AC. Predicted values: how should we use them? Thorax. 1988;43:265-7.
2. Sobol BJ, Sobol PG. Percent of predicted as the limit of normal in pulmonary function testing: a statistically valid approach. Thorax. 1979;34:1-3.
3. Stanojevic S, Wade A, Stocks J, Hankinson J, Coates AL, Pan H, et al. Reference ranges for spirometry across all ages: a new approach. Am J Respir Crit Care Med. 2008;177:253-60.
4. Global Strategy for Asthma Management and Prevention. Global Initiative for Asthma 1. 2011. Disponível em: http://www.ginasthma. org/.
5. Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global Strategy for Diagnosis, Management and Prevention of COPD. Updated 2011 [July 30, 2012]. Disponível em: http://www.goldcopd. org/guidelines-global-strategy-for-diagnosis-management.html.
6. Aggarwal AN, Gupta D, Agarwal R, Jindal SK. Comparison of the lower confidence limit to the fixed-percentage method for assessing airway obstruction in routine clinical practice. Respir Care. 2011;56:1778‑84.
7. Lung function testing: selection of reference values and interpretative strategies. American Thoracic Society. Am Rev Respir Dis. 1991;144:1202-18.
8. Quanjer P, Tammeling G, Cotes J, Pedersen O, Peslin R, Yernault J. Lung volumes and forced ventilatory flows. Report working party standardization of lung function tests, European Community for Steel and Coal. Official statement of the European Respiratory Society. Eur Respir J. 1993;6(Suppl 16):5-40.
9. Pellegrino R, Viegi G, Brusasco V, Crapo RO, Burgos F, Casaburi R, et al. Interpretative strategies for lung function tests. Eur Respir J. 2005;26:948-68.
10. Crapo RO, Morris AH, Gardner RM. Reference spirometric values using techniques and equipment that meet ATS recommendations. Am Rev Respir Dis. 1981;123:659-64.
11. Quadrelli S, Roncoroni A, Montiel G. Assessment of respiratory function: influence of spirometry reference values and normality criteria selection. Respir Med. 1999;93:523-35.
12. Harber P, Tockman M. Defining “disease” in epidemiologic studies of pulmonary function: percent of predicted or difference from predicted? Bull Eur Physiopathol Respir. 1982;18:819-28.
13. Harber P, Schnur R, Emery J, Brooks S, Ploy-Song-Sang Y. Statistical “biases” in respiratory disability determinations. Am Rev Respir Dis. 1983;128:413-8.
14. Oliver LC, Eisen EA, Sprince NL. A comparison of two definitions of abnormality on pulmonary outcome in epidemiologic studies. Am Rev Respir Dis. 1986;133:825-9.
15. Aggarwal AN, Gupta D, Behera D, Jindal SK. Comparison of fixed percentage method and lower confidence limits for defining limits of normality for interpretation of spirometry. Respir Care. 2006;51:737‑43.
16. Swanney MP, Ruppel G, Enright PL, Pedersen OF, Crapo RO, Miller MR, et al. Using the lower limit of normal for the FEV1/FVC ratio reduces the misclassification of airway obstruction. Thorax. 2008;63:1046‑51.
17. Miller MR, Quanjer PH, Swanney MP, Ruppel G, Enright PL. Interpreting lung function data using 80% predicted and fixed thresholds misclassifies more than 20% of patients. Chest. 2011;139:52-9.
18. Gaspar-Marques J, Martins P, Almeida I, Peralta I, Santos S, Serranho S, et al. Função respiratória em idade pediátrica: alterações funcionais e critérios de avaliação. Rev Port Imunoalergologia. 2010;18(Supl.1):23.
19. Guder G, Brenner S, Angermann CE, Ertl G, Held M, Sachs AP, et al. GOLD or lower limit of normal definition? A comparison with expert-based diagnosis of chronic obstructive pulmonary disease in a prospective cohort-study. Respir Res. 2012;13:13.
Submetido em:
25/11/2013
Aceito em:
28/11/2013
Facebook
LinkedIn
Mendeley
StumbleUpon
Reddit
Email