Bronchoalveolar lavage in pediatric patients: are we doing it right?

Abstract

Bronchoalveolar lavage (BAL) is an essential tool for characterizing pediatric pulmonary diseases, but its diagnostic yield is often hampered by technical collection errors and challenges in interpreting results, particularly with the rise of non-culture-based microbiological techniques. Based on a scoped literature review and expert experience, this paper aims to standardize proper BAL technique, detail common procedural mistakes, and establish an updated interpretative framework for pediatric pulmonologists. Understanding these procedural and diagnostic pitfalls is crucial to maximizing the diagnostic utility of BAL and minimizing errors in the management of pediatric lung disease. It is recommended that the subject be taught using a combination of didactic and practical sessions.

Who are the learners?

Pediatric pulmonology fellows from several institutions. We also conduct separate sessions for practicing pediatric pulmonologists who wish to learn advanced bronchoscopy skills.

What is the setting?

The bronchoscopy service at a large pediatric teaching hospital.

What is the context?

For some time, bronchial irrigation was mostly limited to larger-volume therapeutic applications. In 1974 Reynolds and Newball described what became later known as the wedged bronchoalveolar lavage (BAL) technique and performed bronchial lavage analysis for proteins and cells.¹ After the introduction of the flexible bronchoscope into clinical practice, the modern technique of low-volume bronchoalveolar lavage was developed and widely used for diagnostic and research purposes. In the 1970s, Dr. Robert Wood started the journey of pediatric flexible bronchoscopy and described the BAL technique in pediatric patients in 1980.² Over the next years, the cellular and microbiological parameters of pediatric BAL were studied, and the normal standards and principles of diagnostic of lower airway diseases based on BAL analysis were established. Most of the principles of pediatric BAL were adapted from adult pulmonology, and even the latest bronchoscopy guidelines admit that “the optimal manner of performing BAL has not been systematically studied and requires further investigation.”³ The standard descriptions of pediatric BAL techniques leave room for certain controversies, which in our experience are common and may significantly alter the interpretation of the results.

During the last 20 years, the advances of microbiome science have transformed our understanding of the microbiology of the respiratory tract. The complex relationships between upper and lower airway microbiomes were studied. The “non-culture-based” methods, which rely on RNA and DNA sequencing, rapidly evolved and were applied to BAL results interpretation. These more sensitive methods of microbiological assessment changed our understanding of the significance of presence of certain pathogens in BAL and their role in lower airway diseases in children.

Session 1

BAL collection technique

Epithelial lining fluid

The technique of BAL is based on the concept of wedging the bronchoscope into segmental or subsegmental bronchus and flushing of low-volume normal saline, which then irrigates the bronchial tree and reaches the alveoli. The return fluid contains the most valuable substance—epithelial lining fluid (ELF), which carries molecular and cellular components of the respiratory tract. The estimation of the volume of ELF is based on detection of BAL concentration of urea, which easily diffuses into ELF from the plasma, allowing for calculation of ELF volume by diffusion principles. It was shown that 100 mL of adult BAL fluid contains approximately 1 mL of ELF with the rest of the return fluid being infused normal saline (NS).⁴ This number is highly variable and depends on many factors including the volume of infused NS, the power of suctioning, and the dwelling time of NS in the airway, which may cause dilution of ELF if excessive.⁴ This explains why BAL technically does not directly represent ELF but rather a dilution of ELF with NS, which led to various methods of BAL correction including adjusting for protein and albumin,⁵ which was shown to be valuable in standardization of BAL interpretation but has not been widely accepted to clinical pediatric practice.

In addition, the samples of ELF from the central and the distal airway significantly differ in their composition. For example, the distal bronchial samples contain significantly fewer neutrophils and lymphocytes and more alveolar macrophages than the central bronchi.⁶ BAL differentials represent a mixture of proximal and distal airway fluid. Distal wedging is essential to minimize large airway sampling; using a smaller bronchoscope to wedge deeper yields a higher fraction of alveolar fluid, characterized by increased surfactant and lower neutrophil proportions.⁷

BAL volume

There are several important considerations related to BAL volume from adult literature.

First, the cellular BAL composition remains relatively stable in healthy nonsmoking adults⁸ but changes considerably in patients with lung disease depending on the volume of instilled NS. It was shown previously that increase of instillation volume causes reduction of percent of neutrophils in patients with chronic bronchitis⁹ and eosinophils in patients with asthma¹⁰ and increase of percent of lymphocytes in patients with interstitial lung disease.¹¹ Second, the recovery rate of BAL is dependent on several factors. The adult BAL guidelines advise using 100-300 mL of NS for BAL and caution against low recovery rates, which may affect BAL interpretation and consider the pooled volume of BAL <5 mL nonsuitable for interpretation.

The existing pediatric methodological documents admit that there is no uniform agreement on the volume of BAL in children and suggest adjusting it to the child’s weight or functional residual capacity.³ Considering that that volume of ELF/100 mL of BAL in children is higher than in adults, the adjustment of BAL volume by body weight may yield a more constant ELF fraction.¹²

In our daily practice, we infuse total of 1-3 mL/kg of normal saline using 10- to 20-mL aliquots based on the child’s size, typically not exceeding 150 mL. Volumes for neonates and infants may be tailored to clinical stability, though weight-based protocols (3 times by 1 mL/kg) are typically well-tolerated.

Fate of the first aliquot

The most controversy exists around the concept of the “first aliquot.” It contains more columnar epithelial cells, which sometimes is interpreted as “contamination from nasal passages,”¹³ which is not exactly correct, because it could also originate from the bronchial tree.

The “fate” of the first aliquot again depends on the institution’s practice and may vary from completely “dumping” it to, as suggested by ERS guidelines, using it for culture. This last recommendation, though, meets criticism from practitioners who feel that the first aliquot is more representative of proximal airways and less of distal airway and alveoli. However, it was shown that the bacterial load was not significantly different between the first aliquot and pooled BAL, and they contained similar microbiota in children with chronic suppurative lung disease.¹⁴ At our institution, we typically pool all aliquots together. However, in cases of suspected alveolar hemorrhage or pulmonary alveolar proteinosis (PAP), they are analyzed separately. In these conditions, the returned fluid becomes progressively bloodier or “milkier,” respectively. This sequential change occurs because subsequent instillations reach deeper into the alveolar spaces, flushing out higher concentrations of sequestered materials. This principle of mechanical clearance is the basis for therapeutic whole lung lavage, where large-volume saline washes are used to physically remove proteinaceous debris and restore gas exchange in patients with PAP.

Lidocaine controversy

Topical application of lidocaine to upper and lower airway structures is widely used in pediatric bronchoscopy and aims to reduce common complications such as laryngospasm and uncontrollable cough. It is well known that topical lidocaine can reach toxic systemic levels even when is used in the recommended dose range.¹⁵ In addition, topical application of lidocaine was shown to increase both arytenoid and epiglottic components of laryngomalacia, particularly in smaller babies.¹⁶ This important finding should not be ignored by the practitioners performing dynamic upper airway evaluations and drug-induced sleep endoscopy. Finally, there is another important consideration related to its antibacterial effect. Bartlett et al. showed that 2 mL of 2% topical lidocaine without preservative introduced in the trachea during bronchoscopy significantly inhibited growth of Streptococcus pneumoniae and Haemophilus influenzae.¹⁷ More recently, the effect of lidocaine on respiratory cultures was studied by Chandan et al., showing complete suppression of growth of S pneumoniae by 2% lidocaine and 65.5% inhibition by 1%.¹⁸ It is reasonable to adopt the practice of restricting the use of topical lidocaine on the vocal cords to the minimum possible and to refrain from using it below vocal cords to increase the yield of BAL culture.

Suctioning prior to wedging

The contamination of the suction channel of the bronchoscope with oropharyngeal flora is a well-known phenomenon. It may be considerably reduced, bypassing the upper airway, by the introduction of the bronchoscope via an endotracheal tube¹⁹ or use of special protected tip catheter for BAL collection.²⁰ However, presence of an endotracheal tube makes dynamic evaluation of the lower airway impossible, and protected tip catheters are not readily available in some institutions. Another precaution is avoidance of suctioning prior to entering the trachea, which is quite universal for pediatric bronchologists. At the same time, most bronchologists suction from the trachea and main bronchi prior to wedging for BAL to get better visualization of the airway, which in our opinion requires reconsideration. Post et al. showed that suctioning from the bronchial lumen prior to wedging for BAL collection considerably changed the microbial flora of aspirate with poor correlation between wedged and nonwedged samples for Stenotrophomonas maltophilia and Aspergillus fumigatus.²¹ Subsequently it was shown in pediatric patients with bacterial bronchitis that the microbiota of trachea showed significantly higher than BAL sequencing reads, which were approaching ­supraglottic aspirate.²² This difference becomes even more dramatic in children with tracheostomy where the concordance between BAL and tracheal aspirate is very poor.²³ It could be argued that suctioning from the airway prior to wedging leads to unnecessary mixing of tracheal and bronchial microbiota with BAL microbiota and affects the culture results. The challenge associated with “not suctioning before wedging” is that thick, viscous airway secretions can obstruct visualization and make airway navigation difficult. The practical solution is to adapt the technique of insufflation of oxygen or air via the channel to assist in clearing the secretions prior to wedging for BAL.

We should acknowledge that there are clinical situations in which sampling from the large airways is required rather than BAL. Examples include bacterial tracheitis with airway obstruction and purulent bronchitis, the latter of which may warrant both BAL and bronchial washing.

The challenges related to BAL collection are summarized in Table 1.

Table 1.

Challenges with bronchoalveolar lavage collection.

Challenge	Explanation	Practical solution	Comments
Variable amount of ELF in BAL	It depends on the volume of NS, dwelling time, and power of suctioning	Adjusting for protein or albumin Limiting dwell time to 20 seconds (from start of infusion to end of recovery) Limiting power of suctioning to prevent airway from collapsing	Not practical and not used in most pediatric centers Improves ELF recovery
Difference in cellular composition between proximal and distal airway	Higher presence of macrophages in alveoli and neutrophils in bronchi	Wedged BAL	Wedged BAL is a standard care technique
Recovery failure	Insufficient BAL return volume may affect cellular profile and microbiological composition of BAL	Sufficient NS volume Avoid excessive negative pressures during suctioning	The minimally sufficient return BAL volume is not well established in pediatrics
Volume of NS for BAL in children	Volume of ELF/100 mL of BAL in children is higher than in adults.	Adjusting for body weight and using total infused volume of 1-3 mL/kg, usually not exceeding 150 mL	Most centers use 10- to 20-mL aliquots
First aliquot	Often interpreted as “contaminated from upper airway”	Scientific evidence shows that first aliquot has bacterial load and composition like subsequent aliquots	Pool all aliquots together
Lidocaine exposure	Potential for toxicity Increases laryngomalacia Antibacterial effect	Careful dosing Do not use for DISE Limit lower airway exposure	Avoid using below vocal cords to improve bacterial yield of BAL
Suctioning prior to wedging	Significantly changes bacterial composition of BAL, makes difficult differentiation between infection and contamination	Use insufflation of O2 to clear the view	Even suctioning from the bronchial lumen prior to wedging may significantly change microbiological composition of BAL

Abbreviations: BAL, bronchoalveolar lavage; DISE, drug-induced sleep endoscopy; ELF, epithelial lining fluid; NS, normal saline.

Session 2

Interpretation of BAL results

Cells

Determination of total cell counts and differentials in BAL became a standard of care procedure in pulmonology. One of the larger normative studies on this subject was published in 1992 and was based on the BAL analysis in 111 healthy adult volunteers who had never smoked.²⁴ The researchers pointed out the very wide range of cell count norms (2 to 84 × 10⁴ cells/mL). When added to significant variability of cell counts obtained from the same healthy subject several weeks apart,²⁵ the total cell counts most likely have very limited value. This may be related to significant differences in volumes of installed NS and ELF recovery rates as was discussed above.

Alveolar macrophages are the main cell type in the BAL of healthy subjects. It is interesting to note that cytology and hematology laboratories responsible for reporting BAL cellularity often issue the percentages of monocytes along with macrophages, which may be difficult to understand. A more recent study based on single-cell RNA sequencing suggests that alveolar macrophages and alveolar monocytes are 2 different types of cells residing in the air spaces of the healthy lung and may have different phagocytic characteristics and ability to respond to inflammatory and toxic stimuli²⁶; however, the norms for their relative quantities in BAL are not available yet.

The neutrophils and eosinophils may be present in BAL of healthy adults but in very low quantities, while lymphocytes are the most variable cell population, which may change considerably depending on the method of BAL processing including cytocentrifuging, which is performed by most of laboratories.²⁷

There is a paucity of data related to cellularity of BAL in healthy children. Several studies provided basic normal values on cell count and differential of pediatric BAL^28-31 (summarized in Table 2) Similarly to the data in healthy adults, the authors commented on the variability of total cell counts in pediatric BAL and its limited validity in pediatrics. The mean fractions of macrophages, eosinophils, and neutrophils are compatible with healthy adults, while lymphocytes exceeded 20% in one-quarter of studied children, which is higher than reported in adult studies.²⁸

Table 2.

Normal values of cell differential in pediatric bronchoalveolar lavage.

Study	Subjects	Number of subjects	Macrophages	Neutrophils	Lymphocytes	Eosinophils
Ratjen et al.28	Elective surgery	39	81.2 ± 12.7	1.9 ± 2.9	16.2 ± 12.4	0.4 ± 0.6
Midulla et al.29	Stridor	16	85.7 ± 3.4	5.5 ± 2.8	9.3 ± 2.1	0.2 ± 0.1
Koh et al.30	Elective surgery	10	85 (81.5-89.0)	2.3 (1.0-3.9)	7.5 (5.0-10.8)	0.0 (0.0-0.1)
Riedler et al.31	Stridor	18	91.0 (84.2-94.0)	1.7 (0.6-3.5)	7.5 (4.7-12.8)	0.2 (0.0-0.3)
Combineda		83	84.4 ± 10.1	2.7 ± 3.0	12.2 ± 9.8	0.3 ± 0.4

Combined values were calculated with sample-size weighting. Data are reported as mean ± SD or median (25th-75th percentiles).

^aMeans ± SD were estimated from median (25th-75th percentiles) using the Wan/Lou method.

Finally, while ciliated columnar epithelial cells in BAL are often interpreted as “contamination” from the proximal bronchi, several pediatric-specific factors must be considered. The small caliber of pediatric airways makes contact between the bronchoscope and the bronchial epithelium nearly inevitable.³² Furthermore, the mechanical stress of fluid infusion and suctioning can cause excessive sloughing of the epithelial lining. Consequently, using the percentage of epithelial cells as a strict measure of sample quality may be less practical in children than in adults.

Special stains

Lipid quantification in alveolar macrophages is typically performed by Oil Red O staining of 100 consecutive cells, each scored for lipid content to yield a maximum lipid-laden macrophage index (LLMI) of 400. LLMI values >100 have been associated with clinically significant airway aspiration.³³ However, LLMI needs to be interpreted with caution, because it lacks specificity in children with airway inflammation and particularly with cystic fibrosis, likely due to the ingestion of endogenous lipids from bacterial cell walls and neutrophil membranes.³⁴

The Prussian blue staining is used for detection of ferric iron of hemosiderin, the product of degradation of hemoglobin. The presence of hemosiderin in more than 35% of alveolar macrophages is considered reliable evidence of diffuse alveolar hemorrhage in children.³⁵

Of note, hemosiderin-laden macrophages may not be present in BAL yet if it is performed within 50 hours of acute diffuse alveolar hemorrhage, before hemoglobin has metabolized into iron.³⁶

Quantitative cultures

The assessment of bacterial pathogens is one of the most important parts of BAL interpretation. The quantitation of bacterial pathogens became a gold standard of diagnostics for lower respiratory infections since the quantitative technique was suggested and introduced into clinical practice as a reliable method of differentiating between bacterial contamination from the nasal and the oral pharynx and “real” lower airway infections. After exhaustive review of sensitivities and specificities of various threshold values, the consensus was reached to use 10⁴ colony-forming units (CFU)/mL as a proof of lower airway bacterial infection.³⁷ This value was “extrapolated” to pediatric medicine and became widely accepted and recommended by American Thoracic Society pediatric bronchoscopy guidelines³ and eventually validated further by correlating it with inflammatory markers in BAL in children with chronic suppurative lung disease.³⁸ It is important to recognize that the significance of positive bacterial BAL culture should not be judged solely by the quantity of pathogens. The clinical presentation remains of primary importance. For example, there is a notion that even nonquantitative positive BAL cultures may be of significance in immunocompromised children with clinical presentation consistent with lower airway disease.³⁹

Diagnosis of invasive fungal disease via BAL is less standardized than bacterial protocols, and quantitative cultures are generally less reliable and lack diagnostic cutoffs. In immunocompromised patients, any positive fungal culture is typically clinically significant. However, the sensitivity of culture remains low. To improve detection, particularly for invasive pulmonary aspergillosis, cultures should be supplemented with BAL galactomannan testing.⁴⁰

“Normal” oropharyngeal flora

In 1989, Kirkpatrick et al.⁴¹ compared quantitative BAL cultures to protected brush catheter specimens from 8 healthy volunteers and showed that BAL cultures yielded 10 to 10³ CFU/mL of microorganisms in 7 of them, while protected brush culture was positive in only one. The authors concluded that this supported the hypothesis that BAL can be easily contaminated with normal oropharyngeal flora. For several years, presence of oropharyngeal flora in BAL was attributed to contamination and was mostly considered to be clinically insignificant. This situation started to change after emergence of microbiome research with utilization of nonculture 16S rRNA gene metagenomic sequencing techniques. Segal et al.⁴² showed that healthy adults may have 2 different BAL microbiomes, which they called “pneumotypes.” The first pneumotype, similarly to background samples of NS, had high relative abundance of Propionibacterium but the second had high relative abundance of supraglottic-characteristic taxa, such as Prevotella and Veillonella. Remarkably, the second pneumotype was associated with higher numbers of lymphocytes and neutrophils and higher fractional exhaled nitric oxide (FeNO) levels, which may suggest presence of a causal relationship between microaspiration of supraglottic anaerobic flora into the lower airway and inflammation. Later research linked the oral anaerobes Prevotella and Veillonella with airway inflammation in children with protracted bacterial bronchitis.¹⁴ Direct comparison of conventional culture with 16S ribosomal RNA (rRNA) methods was done in a group of children with lower airway diseases and showed that in many cases the pathogens isolated in culture did not dominate the microbial community in the BAL but rather accounted for a relatively small fraction of total lower airway microbiota compared with supraglottic anaerobic flora.²²

BAL cannot be an appropriate specimen for anaerobic culturing due to inevitable mixing of microbial material with air during suctioning and storage. There is an obligatory need for anaerobic transporter with oxidation-reduction indicator, which is not available in most pediatric bronchoscopy centers. Altogether it results in discrepancy between BAL microbiology results obtained by culture-based versus 16S rRNA methods with the culture-based methods underrepresenting lower airway microbiome and reporting it as “oropharyngeal flora.” That is why the appearance of “normal oropharyngeal flora” in the BAL must be interpreted in the clinical context with the understanding that it may represent either contamination of the bronchoscope during the passage through the upper airway, or real colonization/infection of the lower airway with supraglottic anaerobes. There is no reliable method of distinguishing the former from the latter, and quantitation of oropharyngeal flora, although it can be done, does not seem to be clinically rewarding. Regardless, every effort must be made to minimize oropharyngeal and nasopharyngeal contamination of the BAL. Endotracheal tubes or laryngeal mask airways should be prioritized when diagnostic sampling is the primary goal, as they minimize contamination from oropharyngeal flora.³² To further reduce aspiration of oral secretions following anesthesia induction, time between bronchoscope insertion and wedging should be minimized.

Introduction of nonculture methods in clinical practice

BAL culture results are often not available quickly enough to guide urgent clinical decision-making. The introduction of polymerase chain reaction (PCR) testing, specifically the BioFire FilmArray Pneumonia Panel, has revolutionized practice by identifying 18 bacterial pathogens and 7 resistance genes in just 75 minutes. The panel provides semiquantitative estimates (10⁴ to 10⁷ genomic copies/mL) for 15 bacterial targets. Validated against conventional cultures, it demonstrates approximately 90% sensitivity and specificity, allowing for the timely initiation of targeted antibacterial therapy.⁴³

Despite its benefits, this method presents new challenges. It was noticed that the high concordance >90% between quantitative results of PCR and conventional cultures was achieved only with heavy bacterial growth >10⁶ CFU/mL while lower concentrations often yield conflicting results.⁴³ Clinical decision-making is challenging when BAL PCR is positive at low levels (<10⁶ genomic copies/mL), as subsequent cultures often remain negative. These discordant results can result from specific laboratory technologies, poor collection techniques (eg, excessive lidocaine), or the presence of multiple species that inhibit culture growth.⁴³ In addition, there is a notion that treatment with antibiotics prior to bronchoscopy may negatively affect the culture yield in children and increase frequency of PCR-positive/culture-negative results.⁴⁴ This is important when PCR results drive urgent decisions on antibacterial therapy; however, further investigation is required to establish definitive cut-off values for true-positive results. In this respect, the correlation of PCR results with inflammatory profile of BAL becomes of primary importance. The data from an adult study suggest that PCR-positive/culture-negative patients with ventilator-associated pneumonia have higher BAL neutrophil counts than PCR-negative/culture-negative patients,⁴⁵ which puts more diagnostic weight on positive PCR in those cases. On the other hand, a positive PCR result in a patient with normal BAL cellularity may suggest colonization of the lower airway without active infection—the difficult clinical concept particularly important for patients with tracheostomy⁴⁶ but highly likely existing beyond it.

BAL PCR is rapidly advancing and is now recommended for diagnosing invasive aspergillosis in immunocompromised patients.⁴⁷ It also demonstrates satisfactory sensitivity in noninvasive cases. This is particularly valuable in allergic bronchopulmonary aspergillosis, where galactomannan performance is relatively poor.⁴⁸

Metagenomic next-generation sequencing

Metagenomic next-generation sequencing (mNGS) is a relatively new microbiological method now applied to BAL. Unlike targeted PCR, it sequences a sample’s entire genetic content, detecting virtually all pathogens—including rare bacteria—and identifying mixed infections more accurately.

The performance of mNGS varies across studies. In children with complicated pneumonia, mNGS showed higher ­concordance with clinical diagnosis than conventional methods (72% vs 56%).⁴⁹ A 2025 meta-analysis reported an 86% detection rate for mNGS compared to 50% for culture, noting that results depend on extraction methods and patient status.⁵⁰ Remarkably, a negative mNGS result combined with a low BAL neutrophil count (<6%) effectively ruled out infection, potentially aiding antibiotic stewardship.

Despite these advantages, mNGS requires cautious interpretation. Because it detects vast amounts of genetic material, distinguishing between infection, colonization, and contamination is challenging—especially with pathogens not typically associated with lung disease.

In summary, nonculture methods like mNGS are promising. They identify rare pathogens and anaerobic flora while accelerating diagnostic timelines. However, exhaustive validation is required to standardize their application in pediatric patients.

The nonculture methods of BAL interpretation are summarized in Table 3.

Table 3.

Comparison of nonculture methods of bronchoalveolar lavage interpretation.

Method	Description	Pros	Cons
Microbiome research methods	16S rRNA gene metagenomic sequencing techniques	Characterizes full microbiome of the mucosa	Results take a long time Not commercially available
PCR-based methods	PCR amplification	Rapid detection Multiple pathogens Validated and commercially available	Limited pathogen variety Difficulties with interpretation of discrepancies between PCR and culture results
Metagenomic next-generation sequencing	Nucleic acid sequencing of genetic content of a sample	Relatively fast Detection of all pathogens in a sample Improves sensitivity and specificity if used together with conventional culture Increasingly commercially available	No validation in pediatrics yet Difficulties with differentiation between infection, colonization, and contamination

Abbreviation: PCR, polymerase chain reaction.

What is the approach?

Our sessions combine didactic teaching with supervised bronchoscopy procedures. We place special emphasis on potential pitfalls, highlighting the importance of proper techniques for BAL collection. A separate session is dedicated to interpreting the results.

Why is that the approach?

While BAL collection and interpretation are a standard part of pediatric pulmonology training, the curriculum typically pays insufficient attention to the potential pitfalls in these procedures. Supplementing this training with a combination of didactic and procedural bedside teaching is therefore key to improving both bronchoscopy skills and patient outcomes.

What challenges in teaching the material should be anticipated?

We realize this material does not cover every pediatric BAL topic, as a full review would require several textbook chapters. We acknowledge that this teaching material only briefly covers cytology and fungal diagnostics and excludes some important topics such as a detailed review of how BAL cellular profiles vary across different disease processes. Instead, we have focused on the most controversial parts of collection and interpretation. We acknowledge the lack of standard rules and the wide differences in how different hospitals perform this procedure. This guide combines the available research with our 25 years of experience and >7000 procedures. While clinical experience can be subjective, we believe combining data with long-term practice provides a reasonable view.

Conclusion

BAL had been an established method and, in many instances, a gold standard for pediatric airway sampling. The pediatric pulmonary specialists need to be aware of potential errors in BAL technique and interpretation, which may impair clinical decision-making. Further research will be required for standardization of BAL collection and validation of its interpretation, particularly in view of the rapid development of nonculture bacteriological methods.

Supplementary material

Supplementary material is available at ATS Scholar online.

Conflicts of interest

Please see the ICMJE disclosure forms, which have been provided as supplementary material.

Funding

There was no grant or sponsor support or any other financial support for this work.

Disclaimer

The views expressed in this article do not communicate an official position of the NYU Grossman School of Medicine.

Artificial intelligence disclaimer

An AI tool was used for the editing of syntaxis, punctuation, and grammar of the manuscript.