Anticipating undiagnosed asthma in symptomatic adults with normal pre- and post-bronchodilator spirometry: a decision tool for bronchial challenge testing.

BACKGROUND: Some patients with asthma demonstrate normal spirometry and remain undiagnosed without further testing. OBJECTIVE: To determine clinical predictors of asthma in symptomatic adults with normal spirometry, and to generate a tool to help clinicians decide who should undergo bronchial challenge testing (BCT). METHODS: Using random-digit dialling and population-based case-finding, we recruited adults from the community with respiratory symptoms and no previous history of diagnosed lung disease. Participants with normal pre- and post-bronchodilator spirometry subsequently underwent BCT. Asthma was diagnosed in those with symptoms and a methacholine provocative concentration (PC20) of < 8 mg/ml. Sputum and blood eosinophils, and exhaled nitric oxide were measured. Univariate analyses identified potentially predictive variables, which were then used to construct a multivariable logistic regression model to predict asthma. Model sensitivity, specificity, and area under the receiver operating curve (AUC) were calculated. RESULTS: Of 132 symptomatic individuals with normal spirometry, 34 (26%) had asthma. Of those ultimately diagnosed with asthma, 33 (97%) answered 'yes' to a question asking whether they experienced cough, chest tightness or wheezing provoked by exercise or cold air. Other univariate predictors of asthma included female sex, pre-bronchodilator FEV1 percentage predicted, and percent positive change in FEV1 post bronchodilator. A multivariable model containing these predictive variables yielded an AUC of 0.82 (95% CI: 0.72-0.91), a sensitivity of 82%, and a specificity of 66%. The model was used to construct a nomogram to advise clinicians which patients should be prioritized for BCT. CONCLUSIONS: Four readily available patient characteristics demonstrated a high sensitivity and AUC for predicting undiagnosed asthma in symptomatic adults with normal pre- and post-bronchodilator spirometry. These characteristics can potentially help clinicians to decide which individuals with normal spirometry should be investigated with bronchial challenge testing. However, further prospective validation of our decision tool is required.

Between-Visit Variability in FEV1 as a Diagnostic Test for Asthma in Adults.

RATIONALE: The reliability of using between-visit variation in forced expiratory volume in 1 second (FEV1) to diagnose asthma is understudied, and hence uncertain. OBJECTIVE: To determine whether FEV1 variability measured over recurrent visits is significantly associated with a diagnosis of current asthma. METHODS: Randomly selected adults (N = 964) with a history of physician-diagnosed asthma were studied from 2005 to 2007 and from 2012 to 2016. A diagnosis of current asthma was confirmed in those participants who exhibited bronchial hyperresponsiveness to methacholine and/or acute worsening of asthma symptoms while being weaned off asthma medications. Regression analyses and receiver operating curves were used to evaluate the ability of between-visit FEV1 variability to diagnose asthma. RESULTS: A current diagnosis of asthma was confirmed in 584 of 964 participants (60%). Between-visit absolute variability in FEV1 was significantly greater in those in whom current asthma was confirmed, compared with those in whom current asthma was ruled out (7.3% vs. 4.8%; mean difference between the two groups, 2.5%; 95% confidence interval, 1.7-3.3%). However, a 12% and 200-ml between-visit variation in FEV1, which is the diagnostic threshold recommended by Global Initiative for Asthma, exhibited a sensitivity of only 0.17 and a specificity of 0.94 for confirming current asthma. A between-visit absolute variability in FEV1 ≥ 12% and 200 ml increased the pretest probability of asthma from 60% to a posttest probability of 81%. CONCLUSIONS: A 12% and 200-ml between-visit variation in FEV1, if present, has reasonably good specificity for diagnosing asthma, but has poor sensitivity compared with bronchial challenge testing. Between-visit variability in FEV1 is a relatively unhelpful test to establish a diagnosis of asthma.

A clinical tool to calculate post-transplant survival using pre-transplant clinical characteristics in adults with cystic fibrosis.

BACKGROUND: We previously identified factors associated with a greater risk of death post-transplant. The purpose of this study was to develop a clinical tool to estimate the risk of death after transplant based on pre-transplant variables. METHODS: We utilized the Canadian CF registry to develop a nomogram that incorporates pre-transplant clinical measures to assess post-lung transplant survival. The 1-, 3-, and 5-year survival estimates were calculated using Cox proportional hazards models. RESULTS: Between 1988 and 2012, 539 adult Canadians with CF received a lung transplant with 208 deaths in the study period. Four pre-transplant factors most predictive of poor post-transplant survival were older age at transplantation, infection with B. cepacia complex, low FEV1 percent predicted, and pancreatic sufficiency. A nonlinear relationship was found between risk of death and FEV1 percent predicted, age at transplant, and BMI. We constructed a risk calculator based on our model to estimate the 1-, 3-, and 5-year probability of survival after transplant which is available online. CONCLUSIONS: Our risk calculator quantifies the risk of death associated with lung transplant using pre-transplant factors. This tool could aid clinicians and patients in the decision-making process and provide information regarding the timing of lung transplantation.