Sputum induction: review of literature and proposal for a protocol

Airway epithelial overexpressed cathepsin K induces airway remodelling through epithelial-mesenchymal trophic unit activation in asthma

BACKGROUND AND PURPOSE

Airway epithelial cells (AECs) regulate the activation of epithelial-mesenchymal trophic units (EMTUs) during airway remodelling through secretion of signalling mediators. However, the major trigger and the intrinsic pathogenesis of airway remodelling is still obscure.

EXPERIMENTAL APPROACH

The differing expressed genes in airway epithelia related to airway remodelling were screened and verified by RNA-sequencing and signalling pathway analysis. Then, the effects of increased cathepsin K (CTSK) in airway epithelia on airway remodelling and EMTU activation were identified both in vitro and in vivo, and the molecular mechanism was elucidated in the EMTU model. The potential of CTSK as an an effective biomarker of airway remodelling was analysed in an asthma cohort of differing severity. Finally, an inhibitor of CTSK was administered for potential therapeutic intervention for airway remodelling in asthma.

KEY RESULTS

The expression of CTSK in airway epithelia increased significantly along with the development of airway remodelling in a house dust mite (HDM)-stressed asthma model. Increased secretion of CTSK from airway epithelia induced the activation of EMTUs by activation of the PAR2-mediated pathway. Blockade of CTSK inhibited EMTU activation and alleviated airway remodelling as an effective intervention target of airway remodelling.

CONCLUSION AND IMPLICATIONS

Increased expression of CTSK in airway epithelia is involved in the development of airway remodelling in asthma through EMTU activation, mediated partly through the PAR2-mediated signalling pathway. CTSK is a potential biomarker for airway remodelling, and may also be a useful intervention target for airway remodelling in asthma patients.

String test: a potentially useful tool in the diagnosis of pulmonary tuberculosis in Brazilian children and adolescents

This study investigated the potential use of the String Test (ST) for the diagnosis of pulmonary tuberculosis (PTB) in children and adolescents. This is a case series of patients aged 4-15 years presenting with clinically presumed PTB and submitted to ST in three pediatric TB referral centers in Brazil, between November 2017 and July 2020. The ST was performed in the morning, after 4-12 h of fasting, followed by ingestion of the capsule by the patient, which was attached to the patient’s malar region. The material was collected for simultaneous smear microscopy (acid-fast bacilli - AFB), culture and the molecular investigation by the GeneXpert MTB/RIF^®. Thirty-three patients with presumed PTB were included and ST was performed in 26 (78.8%) of them and 7 (21.2%) patients could not swallow the cord. The diagnosis of PTB was established in 11 (42.3%) of the 26 patients who underwent the ST. The diagnosis of PTB was confirmed (by culture or GeneXpert MTB/RIF^®) in 5 patients, 4 of whom were also positive by the ST. Two of them showed positivity by the GeneXpert MTB/RIF^® only in the ST sample. Two other patients had a positive ST following the induced sputum test (AFB, GeneXpert MTB/RIF^®, and positive culture in both specimens). Thus, ST was positive in 36.4% of the patients in whom PTB was diagnosed. ST could be a useful test for diagnosing PTB in children and adolescents.

Determinants of carbon load in airway macrophages in pregnant women

The airway macrophages carbon loading (AMCL) has been suggested to be a biomarker of the long-term exposure to air pollution; however, to date no study has characterized AMCL for the pregnancy period. Therefore, this study aimed to assess the determinants of AMCL during pregnancy in Iran, a middle-income country. This study was based on a sample of 234 pregnant women with term and normal vaginal delivery who were residing in Sabzevar, Iran (2019). We characterized 35 potential determinants of personal exposure to air pollution for each participant, including six personal, nine indoor, and 20 home-outdoor factors. We applied Deletion/Substitution/Addition algorithm to identify the most relevant determinants that could predict AMCL levels. The median (IQR) of AMCL level was 0.12 (0.30) μm² with a successful sputum induction in 82.9% (194) of participants. Ambient residential PM_2.5 levels were positively associated with higher AMCL levels. On the other hand, increased residential distance to the traffic lights, squares and ring-roads, the duration of opening window per day, and opening window during cooking were inversely associated with AMCL levels. Our findings provide novel insights on the different personal, indoor, and outdoor determinants of personal exposure to air pollution during pregnancy in a middle-income country.

Performance of a Real Time PCR for Pneumocystis jirovecii Identification in Induced Sputum of AIDS Patients: Differentiation between Pneumonia and Colonization

Pneumocystis jirovecii pneumonia (PcP) remains an important cause of morbimortality worldwide and a diagnostic challenge. Conventional methods have low accuracy, hardly discriminating colonization from infection, while some new high-cost or broncho-alveolar lavage-based methods have limited usefulness in developing countries. Quantitative PCR (qPCR) tests may overcome these limitations due to their high accuracy, possibility of automation, and decreasing cost. We evaluated an in-house qPCR targeting the fungus mtSSU gene using induced sputum. Sensitivity of the assay (ten target gene copies/assay) was determined using recombinant plasmids. We prospectively studied 86 AIDS patients with subacute respiratory symptoms in whom PcP was suspected. qPCR results were determined as quantification cycles (Cq) and compared with a qualitative PCR performed in the same IS, serum 1,3-β-D-Glucan assay, and a clinical/laboratory/radiology index for PcP. The qPCR clustered the patients in three groups: 32 with Cq ≤ 31 (qPCR+), 45 with Cq ≥ 33 (qPCR-), and nine with Cq between 31-33 (intermediary), which, combined with the other three analyses, enabled us to classify the groups as having PcP, not P. jirovecii-infected, and P. jirovecii-colonized, respectively. This molecular assay may contribute to improve PcP management, avoiding unnecessary treatments, and our knowledge of the natural history of this infection.

Induced sputum abnormalities in gas station attendants

PURPOSE

To investigate inflammatory changes in the induced sputum (IS) of gas station attendants (GSAs) at risk of exposure to fuel vapors through inhalation and susceptible to respiratory complaints and impaired lung function.

METHODS

Hypertonic saline-IS was collected from 52 GSAs who had never smoked (42 men, age = 35.9 ± 8.9 years) and had no known comorbidities. A group of 22 non-smokers (11 men, age = 30.5 ± 5.1 years) selected from the University staff served as control. The GSAs answered a questionnaire and underwent spirometry and chest tomography. A total of 15 inflammatory biomarkers associated with inflammation, including cytokines, chemokines, and mediators of immunological response, were also measured.

RESULTS

The most common symptoms of GSAs were coughing (42.3%) and dyspnea (59.6%) based on the New York Heart Association (NYHA; Class II) classification. Significant elevations (p < 0.05) in forced vital capacity and forced expiratory volume within the first second were observed in the GSAs relative to those in the controls (GSA vs. control: 99 ± 12% vs. 90 ± 9% and 94 ± 11% vs. 87 ± 10%, respectively). The GSAs had a lower percentage of IS lymphocytes than that in the control group (4.5 ± 5.7% vs. 7.7 ± 9.8%). The GSAs also had significantly lower concentrations of IL-4, IL-5, IL-10, IL-12_P70, IFN-γ, and MIP-1α, but IL-3 levels were higher. No differences were observed in the airway thickness and the amount of emphysema between the GSAs and the controls.

CONCLUSION

Despite normal lung function and absence of abnormalities on HRCT, GSAs have a higher frequency of respiratory complaints, with evidence of impairment of lymphocytic activity in the airways.

Effectiveness of inhaled hypertonic saline application for sputum induction to improve Mycobacterium tuberculosis identification in patients with pulmonary tuberculosis

BACKGROUND

This study assessed the effectiveness and diagnostic significance of hypertonic saline sputum induction for improving Mycobacterium tuberculosis (MTB) detection.

METHODS

A prospective, randomized, open, two-arm, comparative study on MTB identification effectiveness when using inhaled sodium chloride hypertonic solution was performed in patients diagnosed with pulmonary tuberculosis (TB). Patients were randomly assigned into two groups: group 1 (inhalation group) included patients who inhaled a 7% sodium chloride solution upon admission to the hospital, and group 2 (control group) coughed up their sputum as usual. For both groups, specimens were tested by bacterioscopic, bacteriological, and molecular genetic methods. Diagnostic chest radiography was performed for all participants.

RESULTS

In this study, 644 patients (mean age 42.2 years; 151 women, 23.4%) were randomly divided into two groups. Low-quality sputum samples were observed in 7.4% of patients from the inhalation group and 28.8% in the control group (p < 0.001). Acid-fast bacilli (AFB) smear was positive in 65.1% of patients from the inhalation group and 51.3% of controls (p = 0.002). A similar statistically significant situation was observed when culture methods (93.9% inhalation group and 81.9% control group, p < 0.001) and molecular genetic tests (92.2% inhalation group and 79.4% control group, p < 0.001) were used. Thus, active pulmonary TB was not verified microbiologically in 6.1% of patients from the inhalation group and in 18.1% of controls (p < 0.001).

CONCLUSIONS

Hypertonic saline sputum induction improves the quality of collected samples. This method may be appropriate to increase the rate of MTB detection in sputum using microscopic, bacteriological, and molecular genetic methods for diagnosing TB on the day of specimen collection. Hypertonic saline sputum induction is suitable for middle- and low-income countries with limited resources and causes no severe adverse effects in TB patients.

Early detection of non-tuberculous mycobacteria in children with cystic fibrosis using induced sputum at annual review

AIM

Non-tuberculous mycobacteria (NTM) have emerged as an important pathogen in cystic fibrosis (CF). Early detection and treatment of NTM can preserve lung function and maintain good lung health. Many children with CF are not regular sputum producers and cough swabs cannot routinely be used to diagnose NTM. We aimed to test the hypothesis that performing sputum induction at routine annual review results in earlier identification of NTM in non-sputum producing children with CF.

METHOD

We conducted a 5-year prospective observational cohort study involving children with CF aged 5-17 years who had sputum induction with hypertonic saline for microbiological surveillance including NTM at their annual review.

RESULTS

Forty-two children (19 males, mean age 11.4 years ± 3.6, mean FEV₁ % predicted 94.7 ± 20.6) participated in the study. Forty-one induced sputum samples from 29 children yielded bacterial pathogens. Six samples from six children (14% of the cohort) yielded NTM never previously isolated from the patient. We also detected three isolates of Pseudomonas aeruginosa and one isolate each of Burkholderia cepacia complex and Meticillin resistant Staphylococcus aureus (MRSA), all of which were first time isolates.

CONCLUSION

We conclude that annual induced sputum for microbiological surveillance is useful for early detection of NTM and other important respiratory pathogens, particularly in non-expectorating children. This may lead to earlier identification and help inform initiation of eradication treatment in children with NTM. Children can also be cohorted earlier, before they potentially infect other children in the clinic.

Environmental and behavioral determinants affecting the association of airway macrophages carbon load with distance to major roads and traffic density

Biomarkers are promising indicators to evaluate human exposure to air pollutants and to predict the health outcomes. Area of Airway macrophages that is occupied by Black Carbon could be used as a biomarker of personal long term exposure to traffic related air pollution. Association of airway macrophages carbon load with weighted average distance and environmental and subject-specific behavior are considered in this study. Sputum samples were taken from 160 healthy adult women and airway macrophages carbon load (AMCL) were determined in 93 subjects, which represent a success rate of 62% in sputum induction. Nearest distance of the subjects to major roads and average weighted distance were calculated for each subject. A questionnaire was field according to general and behavioral characteristics of the participants. There was not any significant difference (P-value >0.05) between induced and non-induced subjects. Subjects with indoor kitchen without separation wall, passive smokers and those with longer presence time in high traffic streets showed higher carbon area. Weighted average distance had a better association (β = -0.186, 95%CI: -0.139, -0.230, P-value = 0.00) with AMCL than nearest distance to major roads (β = -0.155, 95%CI: -0.109, -0.201, P-value = 0.19). Association of Weighted average distance with AMCL was interrupted in subjects with a garage connected to house environment, those with IK kitchen, those with a hood above the stove and passive smokers. The findings indicated that more generation and distribution of indoor air pollutants can completely enhance the internal exposure and indoor pollution has the same importance as outdoor pollution.

Non-invasive early detection of malignant pulmonary nodules by FISH-based sputum test

BACKGROUND

Early detection decreases lung cancer mortality. The Target-FISH Lung Cancer Detection (LCD) Test is a non-invasive test designed to detect chromosomal changes (deletion or amplification) via Fluorescence in situ Hybridization (FISH) in sputum specimens from persons suspected of having lung cancer. We evaluated the performance of the LCD test in patients with highly suspicious pulmonary nodules who were scheduled for a biopsy procedure.

METHODS

Induced sputum was collected from patients who were scheduled for biopsy of a solitary pulmonary nodule (0.8-3 cm) in one of 6 tertiary medical centers in the US and Israel. The lung cancer detection (LCD) Test combined sputum cytology and Target-FISH analysis on the same target cells and the results were compared to the pathology. Participants with non-surgical negative biopsy results were followed for 2 years to determine their final diagnosis.

RESULTS

Of the 173 participants who were evaluated, 112 were available for analysis. Overall, the LCD test had a sensitivity of 85.5% (95% CI, 76.1-92.3), specificity of 69% (95% CI, 49.2-84.7) and an accuracy of 81.3% (95% CI, 72.8-88). The positive and negative predictive values (PPV, NPV) were 88.8% and 62.5%, respectively. The LCD test was positive in 9 of 11 lung cancer patients who had an initial negative biopsy.

CONCLUSIONS

In a cohort of patients with highly suspicious lung nodules, the LCD test is a non-invasive option with good sensitivity and a high positive predictive value. A positive LCD test reinforces the need to aggressively pursue a definitive diagnosis of suspicious nodules.

Efficiency of the Lung Flute for sputum induction in patients with presumed pulmonary tuberculosis

INTRODUCTION

High quality sputum helps increase the sensitivity of the diagnosis of pulmonary tuberculosis.

OBJECTIVES

To evaluate the efficiency of the acoustic device (Lung Flute; LF) in sputum induction compared with the conventional method, hypertonic saline inhalation (HSI).

METHODS

In this crossover study, patients with presumed pulmonary tuberculosis submitted 3 consecutive sputa: the first sputum without induction and the second and third ones using LF and HSI. We compared the efficiency of the 2 induction methods.

RESULTS

Sixty-four participants were eligible. Thirty-five (54.6%) patients had negative smears on the first sputum without induction. Among those patients, 25.7% and 22.9% patients were smear-positive after using LF and HSI, respectively (P = .001). The positive conversion rate was not significantly different between the methods. The first samples without induction yielded 65.7% positive cultures, whereas 71.4% and 77.1% of the samples from LF and HSI were positive, respectively (P = .284). Similar results were observed in the nucleic acid amplification test [no induction (60.0%), LF (72.0%) and HSI (60.0%); P = .341]. In 29 smear-positive patients on the first sputum without induction, we observed no significant increase in smear grade, culture yield and nucleic acid amplification test positivity with either method. LF tended to induce fewer adverse events; desaturation (3.1% vs 11.1%; P = .082) and throat pain (1.5% vs 9.5%; P = .057). LF showed significantly fewer total adverse events (15.8% vs 34.9%; P = .023).

CONCLUSIONS

Our study showed LF had similar sputum induction efficiency to HSI with relatively fewer complications.

Noninvasive effects measurements for air pollution human studies: methods, analysis, and implications

Human exposure studies, compared with cell and animal models, are heavily relied upon to study the associations between health effects in humans and air pollutant inhalation. Human studies vary in exposure methodology, with some work conducted in controlled settings, whereas other studies are conducted in ambient environments. Human studies can also vary in the health metrics explored, as there exists a myriad of health effect end points commonly measured. In this review, we compiled mini reviews of the most commonly used noninvasive health effect end points that are suitable for panel studies of air pollution, broken into cardiovascular end points, respiratory end points, and biomarkers of effect from biological specimens. Pertinent information regarding each health end point and the suggested methods for mobile collection in the field are assessed. In addition, the clinical implications for each health end point are summarized, along with the factors identified that can modify each measurement. Finally, the important research findings regarding each health end point and air pollutant exposures were reviewed. It appeared that most of the adverse health effects end points explored were found to positively correlate with pollutant levels, although differences in study design, pollutants measured, and study population were found to influence the magnitude of these effects. Thus, this review is intended to act as a guide for researchers interested in conducting human exposure studies of air pollutants while in the field, although there can be a wider application for using these end points in many epidemiological study designs.

The Value of Induced Sputum in the Diagnosis and Management of Children with Bronchial Asthma

Background

Induced sputum in children with bronchial asthma represents a non-invasive method of bronchial inflammation assessment. The main objective of our study was to analyze the cellularity of sputum in patients with bronchial asthma according to the level of disease control and the controlling therapy (with/without inhaled glucocorticoids). The second objective was to establish the correlation between sputum cellularity and other indirect parameters used to evidence bronchial inflammation (exhaled nitric oxide) and obstruction (forced expiratory volume in 1 second).

Methods

The study included children with bronchial asthma that were assessed clinically (physical exam, questionnaire on the control of bronchial asthma in children) and by medical tests (induced sputum, exhaled nitric oxide, spirometry).

Results

In patients with partially controlled asthma and those with uncontrolled asthma, the eosinophils percentage in the sputum was higher than in patients with controlled asthma (19.8±26.4% respectively 9.2±20.5% versus 4.5±14.6%, p<0.001). Higher percentage of neutrophils in the sputum was found in the partially controlled and uncontrolled asthma than in the controlled asthma (43.9±20.1% respectively 51.6±38.3% versus 35±19.7%, p=0.009). We also evidenced a direct and statistically significant correlation between the exhaled nitric oxide and the neutrophils percentage in the sputum (r=0.67, p=0.0003). Also, an indirect, moderate to good correlation (r=−0.56, p=0.005) was evidenced between the values of the forced expiratory volume in 1 second and the high eosinophils percentage in the sputum.

Conclusions

In partially controlled and uncontrolled bronchial asthma the eosinophils and neutrophils count in the sputum is significantly higher than in patients with controlled asthma. There is an indirect correlation between the high eosinophils count in the sputum and the forced expiratory volume in 1 second, as well as a direct correlation between the neutrophils count and the exhaled nitric oxide, suggesting that induced sputum should be used in combination with other indirect parameters for the evidence of bronchial inflammation.

A kit to facilitate and standardize the processing of sputum for measurement of airway inflammation

BACKGROUND

The use of inflammometry has been shown to be effective for managing asthma. However, sputum processing can be time consuming. Furthermore, methods of sputum processing can vary among facilities. To help with standardization and to simplify the procedure for laboratory staff, a novel, commercially available processing device (Accufilter, Cellometrics Inc, Canada) has been developed.

OBJECTIVE

To assess the validity of the Accufilter device and kit for recovery of treated specimens, and for quantitative sputum inflammatory cell counts by comparing intrasample measurements with those using the same procedure without the Accufilter device and kit.

METHODS

The present study was a wet laboratory comparison of induced sputum cell counts obtained from sputum processed with versus without the device and kit. Comparisons of each sputum specimen were performed by the same technologist in random order.

RESULTS

A total of 39 samples were processed using both the standard method and the Accufilter device. The intraclass correlation coefficients were high for the weight of the filtrate, and for eosinophil and neutrophil differential counts.

CONCLUSION

A good degree of agreement of results was apparent when the two methods were compared. The differences noted between both methods were minimal and did not modify clinical interpretation. The use of the Accufilter device and kit can be used in place of the standard method for sputum quantitative analysis, especially in centres with large sample loads.

Sputum induction for the diagnosis of pulmonary tuberculosis: a systematic review and meta-analysis

Sputum induction (SI) has been proposed as the optimal sample collection method for patients with paucibacillary tuberculosis (TB). Studies reporting the culture of Mycobacterium tuberculosis from SI were reviewed. A random-effects meta-analysis of diagnostic yield (numerator M. tuberculosis SI culture-positive cases; denominator all culture-positive cases) was conducted. Diagnostic yields (95% confidence intervals, CIs) were displayed as Forest plots. Heterogeneity was evaluated using Chi-squared and I-squared tests and meta-regression analysis. Ninety publications were screened, 28 full-text papers reviewed, and 17 analyzed. Collectively, n=627 SI culture-positive cases among n=975 culture-confirmed TB cases were reported. The diagnostic yield of SI ranged from 35 to 95%. The pooled diagnostic yield was 74% (CI 65-81%), with significant heterogeneity (p<0.0001, I2=86%). There were no statistically significant differences in the yield between sub-groups defined by human immunodeficiency virus (HIV) prevalence or age. Univariate analysis demonstrated that the use of fiberoptic bronchoscopy (FOB) as the comparator method was associated with a 22% reduction (CI 2-42%) in the diagnostic yield of SI. However, after adjustment for confounding, the meta-regression analysis showed that FOB usage (p=0.21) and saline concentration (p=0.31) were not independently associated with the diagnostic yield. SI will detect approximately three-quarters of M. tuberculosis culture-positive cases under study conditions. Significant heterogeneity in the diagnostic yield was not explained by HIV prevalence, age, or the use of FOB as the comparator method. The use of a particular nebulized saline concentration for SI cannot be recommended on the basis of this meta-regression analysis.

Safety and tolerability of sputum induction in adolescents and adults with suspected pulmonary tuberculosis

Sputum induction by the inhalation of hypertonic saline may increase the yield of microbiological diagnosis of pulmonary tuberculosis (TB). This is particularly relevant in paucibacillary TB, such as in children or human immunodeficiency virus (HIV)-infected patients. Sputum induction must be shown to be safe and tolerable in community settings where invasive diagnostic methods are unavailable. The objective of this study was to describe the changes in physiological parameters and adverse events occurring during sputum induction in ambulatory adult and adolescent TB suspects recruited in community clinics. Sputum induction was performed in HIV-infected (n = 35) and HIV-uninfected (n = 67) TB suspects (n = 102). Oxygen saturation (%), blood pressure (mm Hg), heart rate (/minute), respiratory rate (/minute), and adverse events were monitored at baseline, continuously during the salbutamol pre-treatment and saline nebulization phases, and for 30 min afterwards. During nebulization, there was a statistically significant increase in oxygen saturation (1%, p < 0.0001), systolic BP (7 mm Hg, p < 0.0001), and diastolic BP (2 mm Hg, p = 0.008). Post-nebulization decrease in the systolic BP occurred (4 mm Hg, p = 0.016). These changes were not considered to be clinically significant. Eight minor, transitory, self-resolving adverse events occurred (labored breathing, n = 2; chest pain, n = 2; paroxysmal coughing, n = 1; elevated heart rate, n = 1; vomiting, n = 1; hypotension, n = 1), leading to procedure termination in four participants. No serious adverse events occurred. Induced sputum is safe, tolerable, and feasible in adult and adolescent TB suspects in a community healthcare setting.

Determining cystic fibrosis-affected lung microbiology: comparison of spontaneous and serially induced sputum samples by use of terminal restriction fragment length polymorphism profiling

Sampling of the lower airways of the adult cystic fibrosis (CF) lung has received insufficient detailed consideration, with the importance of sampling strategies for bacteriological outcome not known. Although spontaneously expectorated sputum (SES) samples are often used for diagnostic bacteriological analysis, induced sputum (IS) methods have advantages. This study examined whether significant differences in bacterial content were detected when using a culture-independent, molecular profiling technique to analyze SES or IS samples. Moreover, this work examined what trends relating to bacterial species distributions and reproducibility were found in sequentially induced sputum samples and what implications this has for pathogen detection. Terminal restriction fragment length polymorphism (T-RFLP) analysis was performed on a SES sample and 4 subsequent IS samples taken at 5-min intervals from 10 clinically stable, adult CF patients. This was repeated over 3 sampling days, with variability between samples, induction periods, and sampling days determined. A diverse range of bacterial species, including potentially novel pathogens, was found. No significant difference in bacterial content was observed for either SES or serial IS samples. On average, the analysis of a single sample from any time point resolved approximately 58% of total bacterial diversity achieved by analysis of an SES sample and 4 subsequent IS samples. The reliance on analysis of a single respiratory sample was not sufficient for the detection of recognized CF pathogens in all instances. Close correlation between T-RFLP and microbiological data in the detection of key species indicates the importance of these findings in routine diagnostics for the detection of recognized and novel CF pathogens.