Fractional analysis of sequential induced sputum samples during sputum induction: Evidence that different lung compartments are sampled at different time points

doi:10.1016/S0091-6749(99)70374-X

Journal of Allergy and Clinical Immunology

Volume 104, Issue 2, August 1999, Pages 322-328

https://doi.org/10.1016/S0091-6749(99)70374-X Get rights and content

Abstract

Background: The effect of the duration of sputum induction on markers of inflammation in induced sputum is unknown, and the optimal duration of sputum induction for research purposes in airway disease is uncertain. Objective: We sought to determine whether the duration of sputum induction influences the cellular or biochemical characteristics of induced sputum. Methods: Induced sputum was collected sequentially at 4-minute intervals during a 20-minute sputum induction in 12 subjects with mild and moderate asthma. Each 4-minute sample was collected and analyzed separately for total and differential cell counts and for levels of eosinophil cationic protein, fibrinogen, mucin-like glycoprotein, and surfactant protein SP-A. Results: The percentages of eosinophils and neutrophils were significantly higher at the beginning of the 20-minute sputum induction than at the end, whereas the percentage of macrophages was significantly lower at the beginning than at the end. In addition, the levels of eosinophil cationic protein and mucin-like glycoprotein were significantly higher at the beginning of the 20-minute induction than at the end, whereas the level of surfactant protein SP-A was significantly lower. Conclusions: The duration of sputum induction significantly affects the cellular and biochemical composition of induced sputum in a manner suggesting that large airways are sampled at the beginning of sputum induction, whereas peripheral airways and alveoli are sampled at later time periods. Our data demonstrate the importance of standardizing the duration of sputum induction in clinical research studies, and on the basis of these data, we have chosen 12 minutes as the optimal duration for sputum induction in asthmatic subjects. (J Allergy Clin Immunol 1999;104:322-8.)

Section snippets

Subjects

Twelve atopic asthmatic subjects were studied (Table I).

. Clinical characteristics of the study subjects

Subject	Age (y)	Sex	Treatment	FEV₁ (L)	PC₂₀ FEV₁ (% predicted)	FEV₁ methacholine (mg/mL)
1	31	M	B	2.8	70	0.34
2	28	F	B, ICS	3.1	103	0.74
3	29	M	B	2.9	78	1
4	37	F	B	3.2	97	0.13
5	33	M	B	3.4	77	0.18
6	46	F	B, ICS	3.2	100	0.38
7	34	M	B	2.7	73	0.13
8	36	F	B, ICS	2	65	0.36
9	36	M	B	2.8	72	0.52
10	29	M	B	2.9	78	0.18
11	39	F	B	2.4	77	0.41
12	45	F	B	2.5	83	0.18
Mean	35	—	—	2.8	81	0.31^*
*Geometric mean.

B, β-Agonist; ICS, inhaled corticosteroid.

All subjects had been on a stable therapeutic regimen

RESULTS

The volumes of induced sputum were not significantly different for any of the 5 time periods during sputum induction (Fig 1).

. Total cell count, squamous cell percentage, and volume of induced sputum samples collected individually at five 4-minute intervals during a 20-minute sputum induction. None of the changes in these parameters were statistically significant.

In addition, the total cell counts and squamous cell percentages were not significantly different for any of the 5 time periods during

DISCUSSION

The main finding of our study is that the composition of induced sputum changes significantly during sputum induction. Cells associated with airway secretions (eosinophils and neutrophils) were prominent in samples collected early in the induction, whereas cells associated with alveolar secretions (macrophages) were prominent in samples collected later. Similarly, a protein associated with airway secretions (mucin-like glycoprotein) was prominent in samples collected early in the induction,

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Fractional analysis of sequential induced sputum samples during sputum induction: Evidence that different lung compartments are sampled at different time points☆,☆☆

Abstract

Section snippets

Subjects

RESULTS

DISCUSSION

Changes in the cellular profile of induced sputum after allergen-induced asthmatic responses

Am Rev Respir Dis

Cellular and biochemical analysis of induced sputum from asthmatic and from healthy subjects

Am Rev Respir Dis

Non-invasive assessment of bronchial inflammation in asthma: no correlation between eosinophilia of induces sputum and bronchial responsiveness to inhaled hypertonic saline

Clin Exp Allergy

Differences in interleukin-8 and tumour necrosis factor alpha in induced sputum from patients with chronic obstructive pulmonary disease and asthma

Am J Respir Crit Care Med

Comparison of two methods of processing induced sputum: selected versus entire sputum

Am J Respir Crit Care Med

The effect of inhaled leukotriene D4 and methacholine on sputum cell differentials in asthma

Am J Respir Crit Care Med