Noninvasive Tests for Asthma DiagnosisPresentation Transcript
Noninvasive Tests for Asthma Diagnosis & Monitoring BY DR. TAKI ALMOSAWI Mafraq Hospital
LEARNING OBJECTIVES 1) Describe the various non-invasive tests used to diagnose and monitor patients with asthma 2) Discuss the recent advances in the technology of monitoring asthmatic patients 3) Define the difference in the laboratory findings between patients with asthma and with other pulmonary obstructive diseases under different circumstances.
Asthma is a chronic disease affecting 5-10% of population World- wide.
Its incidence has been increasing during the last two decades, especially in the developed countries where it has become the sixth ranking chronic condition and the commonest chronic illness in children.
Despite that, physicians find some difficulties in diagnosis & monitoring of asthma.
Airway inflammation is a central process in asthma
Current management of asthma, is deficient, because it is based on indirect measurements of airway inflammation such as symptoms and lung function.
Symptoms may not accurately reflect the extent of underlying inflammation due to differences in perception.
lung function may be normal in mild asthma, in sub clinical form, & In children.
Early Diagnosis of Asthma is very essential for better management and control
Why Non - invasive measurements?
Specific Non-invasive tests are therefore needed
To assess the type and extent of airway inflammation in individuals in order to help in
A : Diagnosis & differential diagnosis of lung diseases,
B : Assessment of their severity
C : Response to treatment
D : Furthermore, non-invasive tests can be used to investigate the genesis and patho physiological mechanisms of asthma, and to understand different phenotypes of asthma.
Types of Non invasive Methods
Non invasive Methods : include
Pulmonary Function tests: (Spirometery & Peak flow)
Assessment of hyper responsiveness by challenge test with ;Metacholine; histamine; exercise
Assessment of inflammation by measurement of inflammatory markers in
Exhaled air & Breathe Condensate
Non airways based
Pulmonary Function Tests
Measurement of FEV 1 compared to predicted
Improvement of FEV 1 after B 2 antagonist
Change in Peak flow values.
Draw Back of PFT:
Can not be done properly with preschool children
Measurement of hyper responsiveness by challenge test
BHR is a feature of asthmatic inflammation, so its measurement may reflect the asthmatic state. Inhalation of methacholine or histamine is known to provoke bronchospasm in most asthmatics. Increasing concentration are inhaled by the subject until his FEV 1 drops by 20% and the concentration causing this fall (PC20) is recorded and compared with the normal.
Exercise and cold air challenge, have a lower sensitivity.
However, all challenge tests need hospitalization and are nonspecific.
Methacholine Challenge test result of normal and asthmatic patients
Markers of airways inflammation
Exhaled breath contains measurable mediators and Sputum contains cells & mediators. Therefore, Measurement of these biomarkers can be used to assess the degree of airway inflammation.
Two important markers has been utilized for this purpose ;
Exhaled Nitric Oxide in the exhaled air or breathe condensate,
Sputum esinophils count , measurement of eosinophil cells in induced sputum sample
These techniques are completely non-invasive they can be used repeatedly for the serial monitoring, can be used in children &in patients with severe disease
Nitric Oxide Historical view
Nitric oxide has gained attention only around a decade ago, was termed the molecule of the year in 1992
The American scientists who discovered its role in blood vessels relaxation (REF) were awarded The Noble Prize of Medicine in 1998 .
Ferid Murad Louis J. Ignarro Rob. F. Furchgott
NO has been found to be involved in many physiological and pathological processes including inflammation, immunity, vasodilatation and neurotransmission
There are more than 100,000 scientific papers dealing with this remarkable molecule with most of these published within the last five years.
There is probably no pathological condition where nitric oxide does not play an important role.
Its discovery explain the pharmacological action of the Glyceryl tri nitrate and the Viagra
Nitric Oxide Production
Nitric oxide (NO) is synthesized by endothelial , neuronal cells , macrophages and others.
Endogenous nitric oxide is produced from the amino acid L- arginine by the enzyme NO synthase which has three isoforms.
Airway Nitric Oxide, beside being involved in inflammation, serves a variety of pulmonary functions such as vascular and bronchial smooth muscle tone , the ciliary's activity and antiseptic effect.
Source of exhaled nitric oxide
Current thinking is that exhaled NO is derived from the upper and lower respiratory tract ( Airway & alveolar) and diffuses into the lumen by gaseous diffusion down a concentration gradient, thus conditioning exhaled air.
Alveolar NO is Comparatively very low
Several devices are available to measure eNO. All are based on a chemoluminescence technique. Most of the analyzers consist of a sampling system, a computerised NO analyzer with data processing, and user interface. The equipment measures the concentration of NO in sampled air online in parts per billion (ppb) which is equivalent to nano liters per liter (nl/L and displays the calculated data on the monitor
The ATS recommends performing a minimum of three exhaled measures at 0.050 L/s, flow rate within variation of less than 10%
There are several major manufacturers making commercially available analyzers for NO measurements in exhaled breath :
1- NIOX® NO analyzer ( Aerocrine, Sweden ) ,
2- LR2000 analyzer ( Logan Research Ltd, Rochester, UK, )
3- Sievers® NO analyzer ( Ionics Instrument, Boulder, USA, and
4- ECO Physics NO analyzer ( ECOPHYSICS, Duernten, Switzerland )
With technological advances, measurement of ENO may soon make it to the bedside, the emergency room, the physicians office or even at home.
Procedureof eNO measurement
According to the American Thoracic Society (ATS) and European Respiratory Society (ERS) joint recommondation on 2005:
Ref.: Am J Respir Crit Care Med Vol 171. pp. 912-930, (2005).
The patient should be seated comfortably, with the mouthpiece at the proper height and position. The patient inserts a mouthpiece and inhales over 2 to 3 seconds to total lung capacity (TLC), and then exhales immediately,
Two factors need concern : (1) exclusion of nasal NO which can be achieved by exhaling against an expiratory resistance, leading to vellum closure and (2) standardization of exhalation flow rate which can be obtained by slow steady exhalations,(50ml/sec) resulting in a single-breath NO profile .
Online & Offline Measurement of eNO can be done.
Online NO measurement
it refers to a real-time display of exhaled NO breath profiles, where the expired air is continuously sampled by the NO analyzer, and the resultant NO profile is captured and displayed immediately on the monitor
Repeated, reproducible exhalations should be performed to obtain at least three NO plateau values that agree within 10% of each other. Exhaled NO is then calculated as the mean of these values .
In offline testing the gas is collected into suitable receptacles for delayed analysis.
The subject is asked to inhale orally to TLC and then immediately perform a slow vital capacity maneuver against an expiratory resistance into an appropriate reservoir .(The new Mylar balloons allow for sample stability for at least 24-48 hours). The reservoir is sealed and subsequently analyzed for ENO
One of the serious limitations of this approach is the stability of NO in a balloon. Any bacteria colonizing the inner walls of a balloon can substantially increase the NO levels within a short period of time
Importance of NO Measurement
Nitric oxide (NO) is the most extensively studied exhaled marker of airway inflammation,
ENO is a potential surrogate measurement for asthma, as it is elevated in asthmatics, even in preclinical asthma & during remission.
eNO is very sensitive to treatment with (ICS) and can be used to monitor dose-dependent response. It is decreased in steroid responder asthmatics.
eNO level correlates well with tissue eosinophils in the bronchoscopy samples or in sputum.
Although a normal eNO level has not been exactly defined, but a range of 5-16 ppb at a flow rate of 50 mL/s is considered normal by ATS.
In patients with asthma, eNO levels are elevated, above 20 ppb, although there is considerable inter subject variation.
Elevated nitric oxide levels above 30 parts per billion correlated with moderate to severe asthma.
eNO is very sensitive to treatment with (ICS) as it starts decreasing within 6 hours of treatment. eNO level is also reduced by antileukotrienes therapy but not by nedocromil sodium or beta 2-agonists.
(eNO) is useful in monitoring the compliance of (ICS) therapy asthmatic patient.
NO Values in diseases Exhaled nitric coxide (ppb) Before ICS After ICS In patients with (COPD), exhaled NO has been reported to be high in exacerbations compared with stable patients. The increase is derived from alveolar NO Asthmatics
Nasal NO concentrations are very high relative to the lower respiratory tract with the highest levels reported in the paranasal sinuses.
The mean nasal NO level for normal adults and children are 837 ppb & 751 ppb respectively.
Nasal NO may have physiologic roles, such as preserving sinus sterility and modulating ciliary motility.
Nasal NO concentration is elevated in allergic rhinitis and has been proposed as a surrogate marker of nasal inflammation in allergic rhinitis.
In contrast, subjects with primary ciliary dyskinesia and cystic fibrosis have extremely low nasal NO.
Measurement of inflammatory mediators in Exhaled Breath Condensate (EBC) is used to overcome some of the difficulties encountered in exhaled air estimation. The technique is simple, and can be applied to children. The patient breathes into a special plastic tube surrounded by a cold metal sleeve for 10 to 15 minutes. The Breath is condensed in the tube and can be stored in – 20C. The pH in EBC as well as several volatile chemicals (e.g. nitric oxide, carbon monoxide, hydrogen peroxide, ammonia), and non-volatile molecules (e.g. mediators, oxidation products, proteins) may be easily measured later to evaluate the severity of pulmonary inflammation.
Exhaled Breath Condensate
Low pH of exhaled breath condensate, has been reported in asthma and COPD.
In contrast to eNO which is normal in stable COPD and reduced in CF, exhaled carbon monoxide (CO), hydrogen peroxide & nitrite levels in (EBC) are elevated in asthma; COPD , CF and bronchiactesis.
Sputum Eosinophil Count
The evaluation of airway inflammation by examination of induced sputum for cytology and mediators has been found to be a reliable and valid tool in children & adults and correlate well with the more invasive bronchoalveolar lavage in asthma.
Sputum is induced with hypertonic saline . The subject inhales aerosol of hypertonic saline for 15-minute periods and then is encouraged to cough up a sample of sputum which is processed and examined for its cell count. The upper normal limit for sputum eosinophils is 2.5% of non squamous cells in children & 3% in adults. The supernatant fluid of the sample can be used to measure soluble cytokines and other markers of inflammation in sputum.
Standard Protocol for Sputum Induction 8. Stop the procedure after 20 min or if lung function has dropped by 20%. 7. Continue induction for 3 x 5 min . 6. Check FEV1 or, peak expiratory flow every 5 min. 5. Ask the patient to expectorate whenever he feels the need or every 5-min. 4. Begin induction with either 3% or 4.5% saline, and progress to 5% saline, 3. Place a nose clip on the patient's nose. 2. Measure lung function before and 10 min after b2-antagonist is given 1. Pre treat the patient with 200 ug broncho-dilator, b2-antagonist.
Change of Sputum eosinophil after ICS therapy Before ICS After ICS Sputum eosinophil count (%) Asthmatic = 30
Sputum eosinophils appear to correlate well with disease severity, lung function, eNO and BHR, and may be a useful guide to treatment.
Asthmatics treated with ICS show a decrease in their sputum eosinophils and improvement while the persistence of high sputum eosinophils indicates an increased likelihood of a relapse.
eNO & Sputum eosiophils in diseases
Sensitivity and specificity of the diagnostic tests Sensitivity, specificity, and positive and negative predictive values for each of the diagnostic tests for asthma * Some Patient did not complete procedure 88 86 27 * 3 4 * 34 Sputum eosino. > 3% 81 89 25 * 6 3 * 36 eNO > 20 ppb 100 17 32 0 34 7 FEV 1 improvement with steroid > 15% 100 28 32 0 30 11 FEV 1 < 80% predicted 100 0 31 * 0 41 0 Peak flow variation > 20% % % No Yes No Yes Diagnostic test Specificity Sensitivity Non asthma ( n = 32 ) Asthma ( n = 41 ) Disease
Pulmonary Function Tests & ENO PFT is reduced in COPD (eNO) is normal in stable COPD Sensitivities for PFT is (0–47%) Sensitivities with FE NO is (88%) and sputum eosinophils (86%). PFT is NOT useful in monitoring the effectiveness or the compliance of (ICS) therapy in the asthmatic patient useful in monitoring the effectiveness & the compliance of (ICS) therapy PFT is not so sensitive to treatment with (ICS) very sensitive to treatment with (ICS) .Eno Start to decrease, 6 hrs after (ICS) therapy PFT cannot be estimated adequately in mild asthma and in preschool children, it can be estimated in mild asthma and in preschool children Showing normal level before clinical symptoms of asthma & asymptomatic asthmatics Showing increased level in asthmatics even before clinical symptoms & asymptomatic asthmatics Pulmonary Function tests eNO conc. & Sputum eosinophilia
Inflammatory Cell Mediators in serum & urine
Many inflammatory cells produce specific mediators. The level of these mediators in blood, or urine may reflect the activity and turn over of these cells and may be used to assess the inflammatory process. Some of the important mediators are:
Eosinophil cationic protein (ECP) and Eosinophil protein X (EPX) which are used to assess the activity of the eosinophil and their levels in serum, and in urine can be estimated by enzyme linked immunoassay and reflect the severity of inflammation and are associated with severity of asthmatic disease
Leuktrine LTE4 can be estimated in urine and its level is increased in some asthmatics.
Specific IgE antibodies in serum reflect the allergic inflammation
eNO measurement has an enormous potential
as a non-invasive means of monitoring asthma
particular in childhood. The technique is simple, reproducible,and acceptable for patients .
Advances in technology have now resulted in smaller devices that are easier to use and cheaper.
Sputum eosinophilia is very essential marker to reflect airways inflammation and correlate well with disease severity, lung function, eNO and BHR, and may be a useful guide to treatment.
Both eNo & sputum eosinophil can direct better asthma control with ICS and can be used for monitoring the response compliance and determining the tapering of the steroid dose