The potential biases in studying the relationship between asthma and microbial infection

Asthma and risk of glioma: a population-based case-control study

OBJECTIVES

Literature suggests an inconsistent, but largely inverse, association between asthma and risk of glioma, which is primarily due to methodological inconsistency in sampling frame and ascertainment of asthma. The objective of the study was to clarify the association between asthma and risk of glioma by minimising methodological biases (eg, recall and detection bias).

DESIGN

A population-based case-control study.

SETTING

General population in Olmsted County, Minnesota, USA.

PARTICIPANTS

All eligible biopsy-proven incident glioma cases (1995-2014) and two sets of controls among residents matched to age and sex (first set: community controls without glioma; second set: MRI-negative controls from the same community).

METHODS

The predetermined asthma criteria via medical record review were applied to ascertain asthma status of cases and controls. History of asthma prior to index date was compared between glioma cases and their matched controls using conditional logistic regression models. Propensity score for asthma status was adjusted for multivariate analysis.

RESULTS

We enrolled 135 glioma cases (median age at index date: 53 years) and 270 controls. Of the cases, 21 had a history of asthma (16%), compared with 36 of MRI controls (27%) (OR (95% CI) 0.48 (0.26 to 0.91), p=0.03). With MRI controls, an inverse association between asthma and risk of glioma persisted after adjusting for the propensity score for asthma status, but did not reach statistical significance probably due to the lack of statistical power (OR (95% CI) 0.48 (0.21 to 1.09); p=0.08). Based on comparison of characteristics of controls and cases, community controls seem to be more susceptible to a detection bias.

CONCLUSIONS

While differential detection might account for the association between asthma and risk of glioma, asthma may potentially pose a protective effect on risk of glioma. Our study results need to be replicated by a larger study.

Usefulness of asthma predictive index in ascertaining asthma status of children using medical records: An explorative study

BACKGROUND

Frequent wheezing in original asthma predictive index (API) was defined by parental report of recurrent wheezing within 1 year during the first 3 years of life. The nature of frequent wheezing in children, particularly aged over 3 years, has not been studied. We aimed to assess the frequency and interval of wheezing to define frequent wheezing in ascertaining asthma for children using medical records.

METHODS

Among children who participated in a previous study (n = 427), all wheezing episodes documented in medical records were collected for children who had ≥2 wheezing episodes PLUS met one major criterion or two minor criteria of API. We compared the distribution of known risk factors for asthma between subjects having two consecutive wheezing episodes with shorter interval (≤1 year) compared to those with longer interval (1 to 3 years).

RESULTS

A total of 62 children met API at median age of 2.3 years. During follow-up period (median age: 11.3 years), a total of 198 wheezing episodes were observed. 81% of wheezing intervals were within 3 years from the earlier wheezing episode, including 60% within 1 year. Children who met API based on 1-year interval (n = 40) vs 1- to 3-year interval (n = 13) appeared to be similar in regard to the known risk factors for asthma.

CONCLUSIONS

Our exploratory study finding suggests that children who had frequent wheezing episodes with longer interval (<3 years) need to be considered to be determined as asthma cases when API is applied to retrospective medical records. Prospective studies with a larger sample size need to replicate this finding.

Automated chart review utilizing natural language processing algorithm for asthma predictive index

BACKGROUND

Thus far, no algorithms have been developed to automatically extract patients who meet Asthma Predictive Index (API) criteria from the Electronic health records (EHR) yet. Our objective is to develop and validate a natural language processing (NLP) algorithm to identify patients that meet API criteria.

METHODS

This is a cross-sectional study nested in a birth cohort study in Olmsted County, MN. Asthma status ascertained by manual chart review based on API criteria served as gold standard. NLP-API was developed on a training cohort (n = 87) and validated on a test cohort (n = 427). Criterion validity was measured by sensitivity, specificity, positive predictive value and negative predictive value of the NLP algorithm against manual chart review for asthma status. Construct validity was determined by associations of asthma status defined by NLP-API with known risk factors for asthma.

RESULTS

Among the eligible 427 subjects of the test cohort, 48% were males and 74% were White. Median age was 5.3 years (interquartile range 3.6-6.8). 35 (8%) had a history of asthma by NLP-API vs. 36 (8%) by abstractor with 31 by both approaches. NLP-API predicted asthma status with sensitivity 86%, specificity 98%, positive predictive value 88%, negative predictive value 98%. Asthma status by both NLP and manual chart review were significantly associated with the known asthma risk factors, such as history of allergic rhinitis, eczema, family history of asthma, and maternal history of smoking during pregnancy (p value < 0.05). Maternal smoking [odds ratio: 4.4, 95% confidence interval 1.8-10.7] was associated with asthma status determined by NLP-API and abstractor, and the effect sizes were similar between the reviews with 4.4 vs 4.2 respectively.

CONCLUSION

NLP-API was able to ascertain asthma status in children mining from EHR and has a potential to enhance asthma care and research through population management and large-scale studies when identifying children who meet API criteria.

Validation of a questionnaire against clinical assessment in the diagnosis of asthma in school children

AIM

A questionnaire has been used repeatedly in cross-sectional studies to determine the prevalence of asthma, allergic rhinoconjunctivitis (AR) and eczema among schoolchildren in Nordland County, Norway. The current study was designed to validate the questionnaire against clinical assessment as the diagnostic gold standard and to investigate the extent of possible misclassification.

METHODS

A subsample of 801 schoolchildren of 4150, whose parents had answered a questionnaire covering asthma and atopic diseases, underwent a detailed clinical evaluation including a standardized interview, a clinical examination, skin prick tests (SPT), blood samples, spirometry an exercise treadmill test (EIB test) and measurement of exhaled nitrogen oxide (FeNO).

RESULTS

The questionnaire had a sensitivity of 0.96 and a specificity of 0.87 for the diagnosis of asthma ever compared to clinical assessment. The overall agreement (kappa) was 0.80. After clinical assessment the prevalence of asthma ever was adjusted from 17.6 % to 16.9 % (95% CI: 15.8-18.0). The most sensitive and specific questions in identifying asthmatic children by the questionnaire were questions asking about diagnosis ('Has the child ever had asthma?') rather than those covering asthma symptoms such as wheeze, shortness of breath and/or cough. A positive exercise test increased the post-test probability for the asthma diagnosis only to a minimal degree.

CONCLUSION

Based on the good agreement between the questionnaire responses and the clinical assessments, it is concluded that the questionnaire had good validity and served as a useful epidemiological tool. Detailed clinical testing added little additional information.

What does tympanostomy tube placement in children teach us about the association between atopic conditions and otitis media?

Otitis media is the most common infection second only to viral upper respiratory infection in the outpatient setting. Tympanostomy tube insertion (TTI) is the most common ambulatory surgical procedure in the USA. While many risk factors for otitis media have been identified, atopic conditions have been underrecognized as risk factors for recurrent and persistent otitis media. Given that asthma and other atopic conditions are the most common chronic conditions during childhood, it is worth examining the association between atopic conditions and risk of otitis media, which can provide insight into how atopic conditions influence the risk of microbial infections. This paper focuses its discussion on otitis media; however, it is important that the association between atopic conditions and risk of otitis media be interpreted in the context of the association of atopic conditions with increased risks of various microbial infections.

Characteristics of children with asthma who achieved remission of asthma

OBJECTIVE

To characterize two groups of asthmatics who had achieved remission and those who had not achieved remission of asthma.

METHODS

The study was a retrospective cohort study based on 117 asthmatic children who participated in a previous study. We categorized the children into two groups: asthmatics with remission versus asthmatics without remission. We defined remission of asthma as lack of symptoms/signs of asthma or asthma-related medications or health care services for at least three consecutive years. Long-term remission was defined by no relapse of asthma after achieving remission. We characterized these groups.

RESULTS

Of the 117 subjects, 70 (60%) were male, 91 (78%) were Caucasians, and the mean age at index date of asthma was 8.1 years. A total of 59 asthmatic children (50%) achieved remission and 28 asthmatics (24%) achieved long-term remission. Asthmatics with remission were more likely to be Caucasian (87%) compared to those without (69%) (p = .039) There were no differences in the frequency of visits for viral (0.3 vs. 0.4 per person-years, p = .29) or bacterial infections (0.7 vs. 0.5 per person-years, p = .49) between asthmatics with and without remission. Gender, socioeconomic status, smoking exposure, family history of asthma or atopy, breastfeeding history, peak flow meter availability, asthma action plan, and influenza vaccinations were not associated with remission.

CONCLUSIONS

Only half of asthmatic children accomplished remission of asthma ever and 24% of asthmatic children had long-term remission. Ethnicity may affect remission of asthma but microbial infections may not influence the likelihood of remission of asthma and vice versa.

Asthma and proinflammatory conditions: a population-based retrospective matched cohort study

OBJECTIVE

To determine the association between asthma and proinflammatory conditions.

PARTICIPANTS AND METHODS

This population-based retrospective matched cohort study enrolled all asthmatic patients among Rochester, Minnesota, residents between January 1, 1964, and December 31, 1983. For each asthmatic patient, 2 age-and sex-matched nonasthmatic individuals were drawn from the same population. The asthmatic and nonasthmatic cohorts were followed forward in the Rochester Epidemiology Project diagnostic index for inflammatory bowel disease (IBD), rheumatoid arthritis (RA), diabetes mellitus (DM), and coronary heart disease (CHD) as outcome events. Data were fitted to Cox proportional hazards models.

RESULTS

We identified 2392 asthmatic patients and 4784 nonasthmatic controls. Of the asthmatic patients, 1356 (57%) were male, and mean age at asthma onset was 15.1 years. Incidence rates of IBD, RA, DM, and CHD in nonasthmatic controls were 32.8, 175.9, 132.0, and 389.7 per 100,000 person-years, respectively; those for asthmatic patients were 41.4, 227.9, 282.6, and 563.7 per 100,000 person-years, respectively. Asthma was associated with increased risks of DM (hazard ratio, 2.11; 95% confidence interval, 1.43-3.13; P<.001) and CHD (hazard ratio, 1.47; 95% confidence interval, 1.05-2.06; P=.02) but not with increased risks of IBD or RA.

CONCLUSION

Although asthma is a helper T cell type 2-predominant condition, it may increase the risks of helper T cell type 1-polarized proinflammatory conditions, such as CHD and DM. Physicians who care for asthmatic patients need to address these unrecognized risks in asthmatic patients.

Streptococcus pyogenes upper respiratory infection and atopic conditions other than asthma: a retrospective cohort study

BACKGROUND

Patients with asthma have an increased risk of Streptococcus pyogenes infection compared with those without asthma. It is unknown whether this is true for children with other atopic conditions such as atopic dermatitis or allergic rhinitis.

AIMS

To determine the risk of developing S. pyogenes infections of the upper respiratory tract in children and adolescents with atopic dermatitis and/or allergic rhinitis.

METHODS

We conducted a retrospective cohort study that followed a convenience sample of 340 healthy children. Atopic dermatitis or eczema and allergic rhinitis or hay fever were determined based on a physician diagnosis documented in medical records. All laboratory test results of cultures, rapid antigen detection, and polymerase chain reaction tests for S. pyogenes infections during the first 18 years of life were collected to compare the incidence of S. pyogenes infections between children with and without a physician diagnosis of atopic conditions. A Poisson regression was fit to determine the association between asthma and S. pyogenes infections, controlling for other covariates including asthma.

RESULTS

Of the 340 subjects, 327 were eligible for the study. Of these 327 subjects, 143 (44%) had atopic conditions other than asthma. The incidence of S. pyogenes infections in children with atopic conditions other than asthma and those without atopic conditions was 0.24 per person-year and 0.18 per person-year, respectively. The adjusted risk ratios for allergic rhinitis and atopic dermatitis were 1.36 (95% CI 1.07 to 1.66, p=0.011) and 1.30 (95% CI 0.98 to 1.71, p=0.06), respectively, controlling for asthma and other covariates.

CONCLUSIONS

In addition to asthma, allergic rhinitis but not atopic dermatitis is associated with an increased risk of S. pyogenes upper respiratory tract infections.

Influence of asthma epidemiology on the risk for other diseases

Asthma is a multifactorial chronic disease affecting a significant proportion of people in the United States and worldwide. Numerous laboratory and epidemiological studies have attempted to understand the etiology and underlying mechanisms of asthma and to identify effective therapies. However, the impact of asthma on the risk for other diseases has drawn little attention. This paper discusses the potential effects of asthma as a risk factor for other diseases, explores the potential mechanisms, and reviews the implications of the findings to clinical practice, public health, and research.

Assessment of the association between atopic conditions and tympanostomy tube placement in children

This study assesses the relationship between otitis media and atopic conditions in children by comparing the incidence of tympanostomy tube placement between children with and without atopic conditions: asthma, allergic rhinitis, and atopic dermatitis. Study subjects were a cohort of 323 healthy children who participated in a study of vaccine response. All episodes of tympanostomy tube placement and physician diagnoses of allergic rhinitis and atopic dermatitis were collected through comprehensive medical record review. Asthma status was ascertained through application of established criteria. We compared incidence rates of tympanostomy tube placement between children with and without atopic conditions. We fitted data to a Poisson regression model to calculate relative risk ratios (RRs) and their corresponding 95% confidence intervals (95% CI). Three subjects were excluded who did not have parental authorization for using records for research. Of the remaining 320 subjects, 170 (53%) were male subjects, 268 (94%) were white, 124 (39%) were asthmatic patients, and 20 (6%) had tympanostomy tube placement. Children with asthma before the index date of tympanostomy tube placement were more likely to have tympanostomy tube placement compared with those without asthma (RR, 19.33; 95% CI, 11.41; 32.75; p < 0.001). We found a similar association between asthma ever (before or after index date) and the incidence of tympanostomy tube placement (RR, 1.53; 95% CI, 0.93-2.53; p = 0.095). This was true for children with allergic rhinitis compared with those without allergic rhinitis (RR, 1.70; 95% CI, 1.01-2.86; p = 0.007). Atopic dermatitis was not associated with the incidence of tympanostomy tube placement. Asthma or allergic rhinitis may be unrecognized risk factors for recurrent or persistent otitis media. However, given the small sample size of the study, a cohort study with a larger sample size is necessary.

Characterization of the duration from onset of asthma symptoms to asthma disease

BACKGROUND

Little is known about factors associated with progression of childhood asthma from onset of symptoms to index date determined by medical records.

OBJECTIVE

To determine the duration between the onset of asthma symptoms to index date of asthma (ie, time when one met the criteria for asthma) and associated factors.

METHODS

Study participants came from a sample of 839 healthy children, aged 5 to 12 years, who had participated in a previous study. Comprehensive medical record reviews were conducted to determine first documentation of asthma symptoms and index date of asthma. Factors were evaluated for an association with the duration from onset of asthma symptoms to index date of asthma.

RESULTS

Of the study sample, 222 children met the criteria for asthma and had an available onset date of asthma symptoms. The median ages at onset of asthma symptoms and the index date were 5.6 and 7.6 years, respectively. The median duration between onset of asthma symptoms and index date was 2.9 months, and the mean was 17.2 months. There was a tendency for patients with a pet at home (P = .047), exercise-induced symptoms (P = .04), younger age at symptom onset (P = .05), and more severe asthma (P = .05) to have a shorter duration from onset of symptoms to index date.

CONCLUSIONS

The duration from onset of asthma symptoms to index date of asthma varies significantly depending on host and environmental factors. It does not necessarily correlate with commonly recognized risk factors for incidence or severity of asthma.