Disparate diagnostic accuracy of lung function tests as predictors of poor asthma control in children

Detailed characterization and impact of small airway dysfunction in school-age asthma

BACKGROUND

Small airway dysfunction (SAD) is increasingly recognized as an important feature of pediatric asthma yet typically relies on spirometry-derived FEF25-75 to detect its presence. Multiple breath washout (MBW) and oscillometry potentially offer improved sensitivity for SAD detection, but their utility in comparison to FEF25-75, and correlations with clinical outcomes remains unclear for school-age asthma. We investigated SAD occurrence using these techniques, between-test correlation and links to clinical outcomes in 57 asthmatic children aged 8-18 years.

METHODS

MBW and spirometry abnormality were defined as z-scores above/below ± 1.96, generating MBW reference equations from contemporaneous controls (n = 69). Abnormal oscillometry was defined as > 97.5th percentile, also from contemporaneous controls (n = 146). Individuals with abnormal FEF25-75, MBW, or oscillometry were considered to have SAD.

RESULTS

Using these limits of normal, SAD was present on oscillometry in 63% (resistance at 5-20 Hz; R5-R20; >97.5th percentile), on MBW in 54% (Scond; z-scores> +1.96) and in spirometry FEF25-75 in 44% of participants (z-scores< -1.96). SAD, defined by oscillometry and/or MBW abnormality, occurred in 77%. Among those with abnormal R5-R20, Scond was abnormal in 71%. Correlations indicated both R5-R20 and Scond were linked to asthma medication burden, baseline FEV1 and reversibility. Additionally, Scond correlated with FENO and magnitude of bronchial hyper-responsiveness. SAD, detected by oscillometry and/or MBW, occurred in almost 80% of school-aged asthmatic children, surpassing FEF25-75 detection rates.

CONCLUSIONS

Discordant oscillometry and MBW abnormality suggests they reflect different aspects of SAD, serving as complementary tools. Key asthma clinical features, like reversibility, had stronger correlation with MBW-derived Scond than oscillometry-derived R5-R20.

Diagnostic accuracy of peripheral lung function measurements in paediatric asthma control assessment: a pilot study

Introduction

Recent studies have indicated the significance of the peripheral airways in asthma control. Methods estimating airway resistance, air trapping, and ventilation inhomogeneity are useful for assessing this area of the lung and have proven utility in the evaluation of asthma; however, it is unclear which method is most effective at characterising uncontrolled asthma.

Aim

To evaluate the diagnostic accuracy of various peripheral airway function measurements in the assessment of asthma control in children.

Material and methods

Children with controlled (n = 35) and uncontrolled (n = 29) asthma performed a sequence of pulmonary function tests (i.e. spirometry, body plethysmography, oscillometry, nitrogen washout test, and exhaled nitric oxide). The diagnostic accuracy of each peripheral airway measure was evaluated by an area under the receiver operating characteristic curve (AUC).

Results

Most peripheral airway parameters were significantly increased in children with uncontrolled asthma compared with children with controlled asthma. The measures with the highest diagnostic accuracy for asthma control were lung clearance index (LCI) (AUC = 0.76), with high specificity (0.97) and modest sensitivity (0.46), acinar ventilation heterogeneity (Sacin) (AUC = 0.73), with high sensitivity (0.85) and modest specificity (0.54), and resonance frequency (Fres) (AUC= 0.74), with perfect specificity (1.0) but low sensitivity (0.38).

Conclusions

LCI, Sacin and Fres had the highest discriminative capacity for distinguishing children with controlled and uncontrolled asthma among all evaluated peripheral airways measures. Discrepancies in the performance (i.e. sensitivity and specificity) of each parameter suggest that a combination may be most effective in determining asthma control status.

Percent Recovery Index Predicts Poor Asthma Control and Exacerbation in Adults

Background

Previous studies indicate that the percent recovery index (PRI: the percentage increase from the maximally reduced FEV1 after bronchodilator inhalation), one of the indexes of methacholine bronchial provocation, may predict acute asthma exacerbations in childhood and elderly asthmatics. It is known that childhood (<12) and elder (>60) asthmatics may be different to adult patients in many aspect including prognosis. However, in adults, a research for predicting value of PRI to exacerbation is still absence. Besides exacerbation, predicting value of PRI to poor asthma control is also unknown. We try to detect whether PRI can predict poor asthma control and exacerbation in adults in this research. Meanwhile, we try to detect whether treatment can influence PRI.

Methods

In 61 adults with asthma, baseline PRI was measured during enrollment. And then baseline PRI was evaluated as a predictor of exacerbation or poor asthma control at an upcoming 3-month follow-up. The covariates included age, sex, BMI, previous exacerbation, smoking status and baseline lung function. After treatment for 3 months, PRI was measured again and compared with baseline PRI.

Results

After the 3-month follow-up, we found that baseline PRI was significantly related to asthma exacerbation (P = 0.023), poor asthma control (ACT at 3 months, P = 0.014), decreased quality of life (decrease of MiniAQLQ, P = 0.010) and cumulative number of EDHO at 3 months (P = 0.039). Meanwhile, no significant correlation was observed between baseline PRI and inflammation factors (FENO, CaNO, and EOS). Finally, PRI was dramatically reduced after standard treatment for 3 months.

Conclusion

PRI is efficient in the prediction of poor asthma control and exacerbation in adults. The predictive value of PRI may rely on the inherent property of asthmatic airway smooth muscle (ASM) independent of inflammation factors. Effective treatment can alleviate PRI dramatically and that indicate PRI may also be valuable in evaluation of curative effect.

Clinical performance of spirometry and respiratory oscillometry for prediction of severe exacerbations in schoolchildren with asthma

OBJECTIVE

To determine the performance of spirometry and respiratory oscillometry (RO) in the prediction of severe asthma exacerbations (SAEs) in children.

METHODS

In a prospective study, 148 children (age 6-14 years) with asthma were assessed with RO, spirometry and a bronchodilator (BD) test. Based on the findings of spirometry and the BD test, they were classified into three phenotypes: air trapping (AT), airflow limitation (AFL) and normal. Twelve weeks later, they were re-evaluated in relation to the occurrence of SAEs. We analysed the performance of RO, spirometry and AT/AFL phenotypes for prediction of SAEs by means of positive and negative likelihood ratios, ROC curves with the corresponding areas under the curve (AUCs) and a multivariate analysis adjusted for potential confounders.

RESULTS

During the follow-up, 7.4% of patients had SAEs, and there were differences between phenotypes (normal, 2.4%; AFL, 17.9%; AT, 22.2%, P = .005). The best AUC corresponded to the forced expiratory flow between 25% and 75% of vital capacity (FEF_25-75): 0.787; 95% confidence interval, 0.600-0.973. Other significant AUCs were those for the reactance area (AX), forced expiratory volume in the first second (FEV₁), the post-BD change in forced vital capacity (FVC), and the FEV₁/FVC ratio. All of the variables had a low sensitivity for prediction of SAEs. The AT phenotype had the best specificity (93.8%; 95% CI, 87.9-97.0), but the positive and negative likelihood ratios were both significant only for the FEF_25-75. In the multivariate analysis, only some spirometry parameters were significative for prediction of SAEs (AT phenotype, FEF_25-75 and FEV₁/FVC).

CONCLUSIONS

Spirometry performed better than RO for prediction of SAEs in the medium term in schoolchildren with asthma.

Predictive value of impulse oscillometry and multiple breath washout parameters in pediatric patients with cystic fibrosis pulmonary exacerbation

BACKGROUND

Pulmonary exacerbations (PE) tend to complicate the course of cystic fibrosis (CF) and worsen the disease prognosis. One of the diagnostic criteria for an exacerbation is the forced expiratory volume in the first second (FEV₁ ) decline. Not all children, however, are able to perform spirometry. Therefore, the aim of this study was to evaluate alternative lung function tests in the diagnosis of PE.

METHODS

We assessed retrospectively the results of impulse oscillometry (IOS) and lung clearance index in multiple breath washout (MBW) during 259 visits in 47 CF paediatric patients. The differences in the results were compared between patients diagnosed with PE (ΔPE) and those in stable condition (ΔS).

RESULTS

Among the whole group of patients, we found significant differences between the changes during exacerbation (ΔPEs) and stable condition (ΔSs) values for lung clearance index (LCI), S_acin , R5Hz, R5-20Hz, X10Hz, AX, and Fres. The predictive values of Fres and X10Hz in IOS (AUC^ROC 0.71 both parameters) were higher than those of LCI (AUC^ROC 0.67). There was no difference in the predictive values (AUC^ROC ) of Δ LCI and IOS parameters in the subgroups of patients stratified based on FEV₁ z-score cut-off value of -1.64. In both groups of patients, predictive values of LCI were slightly lower than of IOS parameters (AUC 0.66 for LCI vs. 0.69 for both ΔX10Hz z-score and Δ Fres z-score in patients with FEV₁ z-score ≥-1.64 and AUC 0.67 for LCI vs 0.69 for both ΔX10Hz zscore and Δ Fres zscore in patients with FEV₁ <1.64.

CONCLUSIONS

Both IOS and MBW measurements are useful in the assessment of pediatric CF patients with PE. LCI has a similar predictive value to IOS in children with CF independently of their FEV₁ value.

Peripheral airways involvement in children with asthma exacerbation

Objective

The literature provides some evidence of peripheral airways key role in the pathogenesis of asthma. However, the extent to which lung periphery including acinar zone contribute to asthma activity and control in pediatric population is unclear. Therefore, the aim of the study was to estimate peripheral airways involvement in children with asthma exacerbation and stable asthma simultaneously via different pulmonary function tests.

Methods

Children with asthma exacerbation (n = 20) and stable asthma (n = 22) performed spirometry, body plethysmography, exhaled nitric oxide, impulse oscillometry (IOS), and multiple‐breath washout (MBW).

Results

Peripheral airway's function indexes were increased in children with asthma, particularly in group with asthma exacerbation when compared with stable asthma group. The prevalence of abnormal results was significantly higher in asthma exacerbation. All children with asthma exacerbation had conductive ventilation inhomogeneity; 76% had acinar ventilation inhomogeneity. According to IOS measurements, resistance and reactance were within normal range, but other IOS parameters were significantly higher in children with asthma exacerbation compared with stable asthma group. The 36% of children with acute asthma had air trapping.

Conclusion

Significant involvement of peripheral airways was observed in children with asthma, particularly in asthma exacerbation, which determine lung periphery as important additional target for therapy and provide new insights into pathophysiological process of pediatric asthma.

The predictive value of impulse oscillometry for asthma exacerbations in childhood: A systematic review and meta-analyses

OBJECTIVE

Several studies have explored the predictive value of impulse oscillometry (IOS) for asthma exacerbations in childhood, but its specific parameters are still unclear. Therefore, we designed this meta-analysis to determine the related indicators of acute asthma attacks.

METHODS

A comprehensive literature search was performed on July 9, 2020 based on PubMed, Embase, and Web of Science database. Weighted mean differences (WMDs) were calculated using fixed- or random-effects models.

RESULTS

A total of 615 patients from six trials were included in this analysis. IOS may be a useful tool to predict asthma exacerbations. And the results showed that R5 (WMD = -1.21, 95% CI: -1.55 to -0.87, p < .001), Fres (WMD = -1.34, 95% CI: -2.03 to -0.65, p = .018), and AX (WMD = -7.35, 95% CI: -9.94 to -4.76, p < .001) had significant correlation with asthma exacerbations. In addition, X5 may also predict the acute attack of asthma (WMD = 0.81, 95% CI: 0.56 to 1.01, p < .001).

CONCLUSIONS

R5, AX, Fres, and X5 may be able to identify the risk of an acute attack of asthma. Besides, our research further demonstrated that peripheral airway injury may play an important role in the acute attack of asthma.

The roles of impulse oscillometry in detection of poorly controlled asthma in adults with normal spirometry

BACKGROUND

Impulse oscillometry (IOS) has been introduced as a method of assessing asthma control. However, the cutoff IOS values for the detection of asthma control in adults are still unclear.

OBJECTIVE

To assess the diagnostic ability of IOS for distinguishing between poorly controlled and well controlled adult asthmatic subjects with normal spirometry.

METHODS

This cross-sectional study was conducted at the Lung Health Center, Chiang Mai, Thailand, between July 2019 and June 2020. IOS and spirometry were performed in all adult asthmatic subjects but only subjects with normal spirometry were enrolled. Poorly controlled asthma was defined in accordance with the Global Initiative for Asthma (GINA) plus an asthma control test (ACT) score ≤19. A Receiver Operating Characteristic (ROC) curve was plotted to detect poorly controlled asthma using the area under the ROC (AuROC) and 95%CI.

RESULTS

One hundred and forty-two adult asthmatic subjects registering normal spirometry with a mean age of 53.4 ± 15.8 years were enrolled. Eighty-nine (62.7%) subjects were female. IOS parameters including heterogeneity of resistance at 5 Hz and resistance at 20 Hz (R5-R20) and area under reactance (AX) demonstrated excellent detection of poorly controlled asthma with an AuROC of 0.911 and 0.904, respectively. The z-score or absolute value of R5-R20 ≥ 0 and 1 cmH₂O/L/s, respectively, represented the highest AuROC of 0.86, with a sensitivity and a specificity of ≥80.0% for the detection of poorly controlled asthma.

CONCLUSION

IOS is a valuable tool for the detection of poorly controlled asthma in adults with normal spirometry.

Agreement between spirometry and impulse oscillometry for lung function assessment in 6-year-old children born extremely preterm and at term

BACKGROUND

Extremely preterm birth is a risk factor for reduced lung function later in life, and clinical follow-up from early childhood is recommended. Dynamic spirometry is the most widely used method to assess airway obstruction, but impulse oscillometry (IOS) may be an alternative method that is easier to perform in young children. The feasibility and agreement between spirometry and IOS outcome variables has not been investigated in children born extremely preterm.

AIM

To determine the feasibility of and correlation between spirometry and IOS in pre-school children born extremely preterm.

METHODS

Spirometry and IOS were performed in 6-year-old children born extremely preterm (n = 88) and age-matched term controls (n = 84) in Stockholm, Sweden. Correlations between spirometry and IOS outcome variables were analyzed using Pearson's partial correlation, adjusting for height.

RESULTS

Success rate for spirometry (60%) was lower than for IOS (93%) but did not differ significantly between the preterm and term groups (56% and 64% for spirometry, P = .25; and 92% and 94% for IOS, P = .61). Correlations between spirometry and IOS outcomes were at best moderate (Spearman's r = -0.31 to -0.56). Normal IOS identified 69% to 90% of those with normal spirometry. A negative predictive value of 90% was found for R5-R20 versus FEV_0.75 /FVC, suggesting that IOS may be used to exclude obstructive airway disease as measured by spirometry.

CONCLUSION

IOS is a more feasible method than spirometry to assess lung function in young children irrespective of gestational age at birth and could be considered an alternative in children who cannot perform spirometry.