ORIGINAL ARTICLE |
https://doi.org/10.4103/ijrc.ijrc_41_18 |
The Utility of Spirometry in Assessment of Presumptive Diagnosis of Bronchial Asthma in a Nigerian Tertiary Hospital
Department of Medicine, University of Nigeria Teaching Hospital, Enugu, Departments of 1Medicine and 2Paediatrics, College of Medicine, University of Nigeria, Nsukka, Nigeria
E-mail: nnamnwosu@yahoo.com
Abstract
Context: Spirometry with reversibility testing is the gold standard for definitive diagnosis of bronchial asthma. However, even in those with established bronchial asthma reversibility test result may subsequently become negative. Spirometry results may also be normal during exacerbation-free intervals. Aims: This study assessed the role of spirometry in diagnostic evaluation of bronchial asthma and determined the ventilatory patterns of patients with presumptive diagnosis of bronchial asthma using spirometry and the proportion of those who showed positive reversibility test. Patients and Methods: This was a retrospective study carried out at a teaching hospital in Nigeria. This was an audit of consecutive patients with presumptive diagnosis of asthma referred for spirometry between January 2013 and June 2015. Spirometer with disposable mouthpieces, stadiometer, and salbutamol inhalers were used. The statistical analysis was done with Statistical Package for the Social Sciences version 20. Results: Eighty-nine participants did spirometry of whom 28 (31.5%) had additional postbronchodilator testing. Fifty (56.3%) participants were females (mean age of 42.17 ± 15.48 years). Normal, obstructive, restrictive, and mixed ventilatory patterns were found in 39 (43.8%), 31 (34.8%), 10 (11.2%), and 9 (10.1%) participants, respectively. Positive reversibility test result occurred in 15 (53.6%) participants, 9/19 obstructive (47.4%), and 6/9 mixed patterns (66.7%). Conclusion: Only a few patients with presumptive diagnosis of asthma were confirmed by spirometry. Spirometry is useful in asthma diagnosis, but clinicians should be aware of its limitations in diagnostic assessment. Although asthma is typically associated with obstructive spirometry, other spirometry patterns can occur.
Keywords: Mixed pattern, obstructive, postbronchodilator test, prebronchodilator test, restrictive, ventilatory pattern
How to cite this article: Nwosu NI, Chukwuka CJ, Onyedum CC, Odilinye HC, Nlewedim PI, Ayuk AC. The utility of spirometry in assessment of presumptive diagnosis of bronchial asthma in a Nigerian tertiary hospital. Indian J Respir Care 2019;8:102-6.
Received: 09-09-2018
Revised: 16-10-2018
Accepted: 21-01-2019
INTRODUCTION
Asthma prevalence is rising worldwide.[1,2] Symptom-based diagnosis and management of asthma are inadequate but widely practiced in Nigeria.[3] This can lead to overdiagnosis and unnecessary exposure to medications and their side effects.[4–7] Spirometry is recommended as essential in the diagnosis of asthma.[8,9] Management of patients whose asthma diagnosis later changes to chronic obstructive pulmonary disease (COPD) following spirometry has significant clinical implications.[10]
Spirometry is infrequently used for the diagnosis of asthma in Nigeria and is confined mainly to tertiary hospitals.[3,11-15] This study determined the ventilatory patterns in asthma and identified subsets of patients with spirometry-confirmed asthma and COPD.
PATIENTS AND METHODS
Consecutive adult patients with presumptive diagnosis of asthma, who had spirometry between January 2013 and June 2015, were retrospectively studied. Approval for this study was obtained from the ethics committee of our hospital. Patient's data gathered included biodata, anthropometry, and details of the ventilatory measurements.
A presumptive diagnosis of asthma was made by either a senior registrar or a consultant physician, if the patient had recurrent symptoms of asthma such as cough, chest tightness, dyspnea, and/or wheezing and if history-taking, examination, and investigations had ruled out differential diagnoses of asthma. As such, pulmonary tuberculosis, pneumonia, upper respiratory tract infections, congestive cardiac failure, and interstitial lung diseases were variously ruled out on case-by-case basis.
All spirometry tests were done using Spirolab III (Medical International Research, Via del Maggiolino, 12500155 Rome, Italy) and conducted by respiratory physicians and trained residents attached to the respiratory unit of the hospital. Spirometry maneuver and interpretation were done according to Global Initiative on Chronic Lung Disease and American Thoracic Society and European Respiratory Society (ERS) guidelines.[16–18]
Accordingly, ventilatory functions were classified as normal when both forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were >80% predicted for race, height, age, and sex and FEV1/FVC was >70%; obstructive pattern if FEV1/FVC was < 70%; restrictive pattern if FEV1/FVC was >70% with FEV1 and/or FVC <80% predicted; and mixed pattern if FEV1/FVC was <70% and both FEV1 and FVC were <80% predicted. ERS reference values were used, and a correction factor of 10% was applied to adjust for our African study population.
Reversibility testing was done if prebronchodilator spirometry was of obstructive or of mixed pattern, with 400 mcg of inhaled salbutamol, and was considered positive if postbronchodilator FEV1 or FVC was 200 ml and 12% above prebronchodilator values. Spirometry confirmation of asthma was based on positive reversibility testing. Participants who had obstructive spirometry with no record of reversibility testing were excluded [Figure 1].
Data analysis was done with Statistical Package for the Social Sciences version 20 (SPSS Inc., Chicago, IL, USA).
Figure 1: Flow chart showing the final diagnosis by spirometry for patients' clinically diagnosed asthma, chronic obstructive pulmonary disease
Descriptive statistics (frequency and percentages) were used to analyze the age and sex. Data are presented in tables and charts.
RESULTS
Eighty-nine patients had prebronchodilator spirometry, comprising 50 females (56.2%) and 39 males (43.8%) [Table 1]. Their age ranged from 18 to 78 years, with a mean of 42.17 ± 15.48 years. Thirty-nine (43.8%) patients had normal ventilatory pattern, 31 (34.8%) showed obstructive pattern, 10 (11.2%) were restrictive, while 9 (10.1%) showed mixed pattern [Figure 2]. Further, postbronchodilator spirometry was performed on those who had obstructive or mixed ventilatory pattern (28 participants [19 prebronchodilator obstructive and 9 prebronchodilator mixed patterns]). Nine participants out of the 19 (47.4%) patients with prebronchodilator obstructive pattern and six out of the 9 (66.7%) patients with prebronchodilator mixed pattern (total of 15 [53.5%]) demonstrated positive reversibility test result [Figure 3].
DISCUSSION
This study showed that all types of spirometric patterns (normal, obstructive, restrictive, and mixed in decreasing order of frequency) were present in patients with presumptive diagnosis of asthma. Miller and Palecki in their study made a similar observation that all four different spirometric patterns (44% obstructive, 26% normal, 24% restrictive, and 6% mixed) occurred in their 413 asthma patients.[19] In that study, the diagnosis of asthma was made on the basis of typical symptoms of asthma in addition to the presence of repeated variability in well-performed spirometric values or positive bronchodilator response or positive methacholine challenge test.
| Age range (years) | Male, n (%) | Female, n (%) | Total, n (%) |
|---|---|---|---|
| 18-20 | 1 (2.6) | 3 (6.0) | 4 (4.5) |
| 21-30 | 11 (28.2) | 11 (22.0) | 22 (24.7) |
| 31-40 | 9 (23.1) | 12 (24.0) | 21 (23.6) |
| 41-50 | 4 (10.3) | 10 (20.0) | 14 (15.7) |
| 51-60 | 10 (25.6) | 6 (12.0) | 16 (18.0) |
| >60 | 4 (10.3) | 8 (16.0) | 12 (13.5) |
| Total | 39 (100.0) | 50 (100.0) | 89 (100.0) |
X2=5.051, P=0.410
Figure 2: Pattern of prebronchodilator ventilatory function in patients with presumptive diagnosis or bronchial asthma
Figure 3: Reversibility test results (positive or negative) for participants with prebronchodilator obstructive and mixed ventilatory patterns
In this study, 19% (15/77) had definitive confirmation of asthma diagnosis based on a positive reversibility test result. This was in consonance with the findings by Decramer et al., who confirmed asthma in 13% (55/435) of their study participants after a positive reversibility testing.[20] In their study, 50 more patients were further diagnosed with asthma after additional investigations (absolute lung volume assessment, airway resistance, and diffusing capacity of carbon monoxide [DLCO]) were carried out. More importantly, a further 264 patients were diagnosed with asthma after exhaled nitric oxide and histamine provocation tests. Asthma was eventually ruled out in only 66 (15%) of their study population. Thus, asthma was confirmed by bronchodilator spirometry test in only 13% and by using other investigative modalities in 72%. Their study findings as well as our findings show the limitation of merely using bronchodilator spirometry even though it is considered as “gold standard” in asthma diagnosis. Due to lack of further investigative tools, we were unable to determine whether the participants in our study who did not have positive reversibility results could still be asthma cases and what percentage were truly “false positives” that did not need the asthma medications they were already receiving.
Schneider et al.,[21] in Germany, reported a low sensitivity of 29% and a specificity of 90% in diagnosing airway obstruction in asthma using spirometry. They estimated the pretest probability of asthma as being 45%. While the positive predictive value (PPV) was 77%, they found a relatively low negative predictive value (NPV) of 53% in their population, indicating that normal spirometry result does not rule out asthma. With a lower prevalence of asthma in Nigeria[22] of 12%, the PPV and NPV after spirometry test in Nigeria would be 28% and 90%, respectively, based on Bayes' theorem.[23] This means that more Nigerian patients who test negative (normal spirometry) are more likely truly negative than the German patients or those in countries with higher prevalence.
Nearly one-half of our study participants had normal ventilatory pattern. These may possibly be explained by lack of airway obstruction at the time of spirometry due to the variability in asthma, prior use of asthma medications, or those presenting with symptoms of asthma caused by other unrecognized asthma mimics, such as upper airway cough syndrome, anxiety causing dyspnea, and deconditioning. It has been suggested that a single spirometry test is not sufficient in making a definitive diagnosis of asthma.[24] Nevertheless, our patients were placed on asthma medications before or after the first spirometry making the likelihood of obstructive spirometry results on subsequent visit very slim, except in circumstances of renewed exacerbation.
In the study by Schneider et al.,[21] where they used bronchodilator spirometry, methacholine challenge tests, and whole-body plethysmography as investigative tools, 219 participants who had symptoms in keeping with obstructive airway disease were diagnosed to have asthma (41.1%) or COPD (22.8%) or neither of the two conditions (36.1%). Bronchial challenge test with methacholine to elicit bronchial hyperresponsiveness is considered by some authors as the best method to diagnose asthma,[25] and they would proceed to subjecting participants with normal ventilation to bronchial challenge test using methacholine. We were, however, unable to do this.
We also did not conduct reversibility test on our participants with normal spirometry as this was not recommended in the guidelines.[16–18] However, Hegewald et al. have shown that patients with normal spirometry could have positive reversibility test result. Of 1394 participants with normal spirometry in their study, 3.1% showed positive reversibility test, but the study did not mention the various indications for spirometry for those patients.[26]
Just over half of the participants with prebronchodilator obstructive pattern and few with mixed pattern in our study failed to show positive reversibility test, leading to an alternative diagnosis of COPD. However, it is known that the lack of acute improvement with bronchodilator inhalation during reversibility testing does not completely rule out asthma, especially when the history is more suggestive of asthma rather than COPD.[27] Furthermore, chronicity of asthma with airway remodeling may lead to poor reversibility results, and this may explain the observation in some of our study participants.[28]
Positive reversibility test result noted in some of our study participants confirmed asthma. It is also known that positive reversibility although rare may also occur in patients with COPD and a subset of patients known as asthma-COPD overlap syndrome.[29] However, additional history and lung function measurements in keeping with COPD help distinguish it from asthma. Unlike in asthma, postbronchodilator FEV1/FVC in COPD is expectedly <70%.
Using a fixed FEV1/FVC ratio of <70% obstructive or mixed ventilatory pattern was noted in a third of our study participants. The pattern may have been slightly different if the more current global lung function initiative equation was used, which defines obstructive ventilation as FEV1/FVC ratio below the lower limit of normal, that is, the 5th percentile of the predicted value.[30]
Restrictive pattern was found in a fifth of our study participants These may be a reflection of early airway closure with air trapping as seen in severe airway obstruction occurring in asthma whereby FVC is greatly reduced leading to false normalization of FEV1/FVC ratio.[31,32] This can also result from failure to exhale sufficiently to empty the lung.[17] With whole-body plethysmography, this distinction can be further made between true and false restrictive pattern. In work by Miller and Palecki, in 413 patients with confirmed asthma, 100 (24%) were noted to have a restrictive pattern.[19] They attributed the restrictive pattern to obesity with body mass index (BMI) >30 and/or decreased DLCO in 68 (16%) participants and to asthma in 32 (8%) in whom BMI and DLCO were within normal range. Only seven participants (2%) had pseudorestriction in that cohort. True restriction in asthma patients is reported to be due to the closure of the terminal lung units by contraction of alveolar ducts.[32] In a study by Keddissi et al., in Oklahoma, USA,[32] among 7502 patients referred for spirometry with provisional diagnosis of asthma and COPD, 21 showed reversible restrictive spirometry, of whom 33% was true restrictive. The remaining 67% was pseudorestriction attributed to air trapping.
Our study had some limitations. Excluding those who did not receive or had a record of postbronchodilator spirometry may have affected our result. We, however, reported what was available in the patients' spirometry records. We did not assess for variability in lung function by conducting serial spirometry on the same patients. Furthermore, we could not carry out further investigation to confirm asthma on patients that showed negative bronchodilator reversibility.
CONCLUSION
Spirometry is useful in confirming diagnosis of asthma, but clinicians should be aware that normal spirometry does not confidently rule out asthma, and that follow-up spirometry may be needed to further evaluate asthma patients with normal spirometry result. We suggest that further research using other diagnostic tools for asthma should be undertaken to understand their relative utility in asthma diagnosis compared to spirometry.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| Access this article online | |
Quick Response Code:
|
Website: |
REFERENCES
1. Oni AO, Erhabor GE, Egbagbe EE. The prevalence, management and burden of asthma - A Nigerian study. Iran J Allergy Asthma Immunol 2010;9:35-41.
2. Global Asthma Network. Global Asthma Report; 2014. Available from: Replace highlighted text with http://www.globalasthmanetwork.org/publications/Global_Asthma_Report_2014.pdf. [Last accessed on 2018 Aug 09].
3. Ayuk A, Iloh K, Obumneme-Anyim I, Ilechukwu G, Oguonu T. Practice of asthma management among doctors in South-Eastern Nigeria. Afr J Respir Med 2010;6:14-7.
4. British Thoracic Society, Scottish Intercollegiate Guidelines Network. British Guideline on the Management of Asthma: A National Clinical Guideline. Edinburgh, UK: National Health Service Quality Improvement Scotland; Thorax 2018;63 Suppl 4:iv1-121. doi: 10.1136/thx.2008.097741.
5. Aaron SD, Vandemheen KL, Boulet LP, McIvor RA, Fitzgerald JM, Hernandez P, et al. Overdiagnosis of asthma in obese and nonobese adults. CMAJ 2008;179:1121-31.
6. Metha C, Migliore C, Rezai F, Patel L, Anandarangam T, Karetzky M. Over-diagnosis of asthma and its relationship to body mass index. Chest 2006;130:97S.
7. Koffi N, Kouassi B, Ngom AK, Kone MS, Danguy EA. Evaluation of management of asthma African adults. National survey among general physicians from Ivory Coast. Rev Mal Respir 2001;18:531-6.
8. National Asthma Education and Prevention Program. Expert panel report 3 (EPR-3): Guidelines for the diagnosis and management of asthma-summary report 2007. J Allergy Clin Immunol 2007;120:S94-138. Erratum in: J Allergy Clin Immunol 2008;121:1330.
9. Reddel HK, Taylor DR, Bateman ED, Boulet LP, Boushey HA, Busse WW, et al. An Official American Thoracic Society/European Respiratory Society Statement: Asthma control and exacerbations: Standardizing endpoints for clinical asthma trials and clinical practice. Am J Respir Crit Care Med 2009;180:59-99.
10. Walker PP, Mitchell P, Diamantea F, Warburton CJ, Davies L. Effect of primary-care spirometry on the diagnosis and management of COPD. Eur Respir J 2006;28:945-52.
11. Oni OA, Erhabor GE, Oluboyo PO. Does health-related quality of life in asthma patients correlate with the clinical indices? S Afr Fam Pract 2014;56:133-8.
12. Desalu OO, Salami AK, Fawibe AE, Oluboyo PO. An audit of spirometry at the university of Ilorin teaching hospital, Ilorin, Nigeria (2002-2009). Ann Afr Med 2010;9:147-51.
13. Adeyeye OO, Bamisile RT, Brodie-Mends AT, Adekoya AO, Bolarinwa FF, Onadeko BO, et al. Five-year audit of spirometry at the LASUTH, Ikeja, South-West Nigeria. Afr J Respir Med 2012;8:15-7.
14. Onyedum CC, Chukwuka CJ. Indications for spirometry at a tertiary hospital in South East, Nigeria. Niger J Clin Pract 2009;12:229-31.
15. Osaretin OW, Uchechukwu ND, Osawaru O. Asthma management by medical practitioners: The situation in a developing country. World J Pediatr 2013;9:64-7.
16. Global Initiative for Chronic Obstructive Lung Disease. Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease; Am J Respir Crit Care Med 2007;176:532-55.
17. 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.
18. Miller MR, Hankinson J, Brusasco V, Burgos F, Casaburi R, Coates A, et al. Standardisation of spirometry. Eur Respir J 2005;26:319-38.
19. Miller A, Palecki A. Restrictive impairment in patients with asthma. Respir Med 2007;101:272-6.
20. Decramer M, Janssens W, Derom E, Joos G, Ninane V, Deman R, et al. Contribution of four common pulmonary function tests to diagnosis of patients with respiratory symptoms: A prospective cohort study. Lancet Respir Med 2013;1:705-13.
21. Schneider A, Gindner L, Tilemann L, Schermer T, Dinant GJ, Meyer FJ, et al. Diagnostic accuracy of spirometry in primary care. BMC Pulm Med 2009;9:31.
22. Onyedum C, Ukwaja K, Desalu O, Ezeudo C. Challenges in the management of bronchial asthma among adults in Nigeria: A systematic review. Ann Med Health Sci Res 2013;3:324-9.
23. Peacock JL, Peacock PJ. Oxford Handbook of Medical Statistics. 1st ed. New York: Oxford University Press Inc.; 2013. p. 234.
24. Kaplan A, Stanbrook M. Must family physicians use spirometry in managing asthma patients? YES. Can Fam Physician 2010;56:126, 128, 130,132.
25. Hunter CJ, Brightling CE, Woltmann G, Wardlaw AJ, Pavord ID. A comparison of the validity of different diagnostic tests in adults with asthma. Chest 2002;121:1051-7.
26. Hegewald MJ, Townsend RG, Abbott JT, Crapo RO. Bronchodilator response in patients with normal baseline spirometry. Respir Care 2012;57:1564-70.
27. Enright PL, Studnicka M, Zielinski J. Spirometry to detect and manage chronicobstructive pulmonary disease and asthma in the primary care setting. Eur Respir Monogr 2005;31:1-14.
28. Karkhanis VS, Joshi JM. Spirometry in chronic obstructive lung disease (COPD). J Assoc Physicians India 2012;60 Suppl: 22-6.
29. Global Initiative for Asthma. GINA Global Strategy for Asthma Management and Prevention. Global Initiative for Asthma; 2015. Available from: http://www.ginaasthma.org. [Last accessed on 2018 Aug 09].
30. Quanjer PH, Stanojevic S, Cole TJ, Baur X, Hall GL, Culver BH, et al. Multi-ethnic reference values for spirometry for the 3-95-yr age range: The global lung function 2012 equations. Eur Respir J 2012;40:1324-43.
31. Al-Ashkar F, Mehra R, Mazzone PJ. Interpreting pulmonary function tests: Recognize the pattern, and the diagnosis will follow. Cleve Clin J Med 2003;70:866, 868, 871-3.
32. Keddissi JI, Elya MK, Farooq SU, Youness HA, Jones KR, Awab A, et al. Bronchial responsiveness in patients with restrictive spirometry. Biomed Res Int 2013;2013:498205.
________________________
© 2019 Indian Journal of Respiratory Care. This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.