Diagnostics
Diagnostics at the Institute for Respiratory Diseases Medaimun
The Institute for Respiratory Diseases "Medaimun" is equipped with state-of-the-art medical technology and equipment, enabling comprehensive diagnostics in the fields of allergology and pulmonology. In addition, the knowledge and experience of the medical staff under the leadership of Prof. Dr. med. Zielen are at your disposal. In the following article, you can learn more about the diagnostics at our Institute for Respiratory Diseases "Medaimun." For an examination and consultation, during which the diagnostic measures listed below may be used, you can schedule an appointment online here.
Content
Allergy test on the skin
The prick test for standard allergens (birch, alder, hazel, ash, mugwort, ragweed, plantain, grasses, rye, house dust mites (D. pteronyssinus, D. farinae), mold (Cladosporium, Alternaria, Aspergillus), dog, horse, and cat hair epithelia), egg, milk, and peanut is performed as usual. The control substances histamine and saline, as well as the allergens, are applied to the skin on the forearm's extensor surfaces.
Next, the skin is lightly scratched with a lancet. After 15 minutes, the test is read. A positive test is indicated if the diameter of the histamine or allergen wheal is greater than 3 mm.
According to the guidelines, antihistamines such as cetirizine and desloratadine should be discontinued for at least 48 hours, preferably 7 days, before the test.
Measurement of exhaled nitric oxide (eNO)
The measurement of exhaled eNO in exhaled breath is a method for assessing the progression of bronchial inflammation, e.g., in allergic asthma.
In the conducted tests, the NO concentration in the exhaled breath is determined using a chemiluminescence analyzer (NIOX Vero®, Circassia, Germany).
To make this test easily performable for children, a computer animation with a flying balloon is used. The patients are asked to exhale evenly into the device for 10 seconds, and children for 6 seconds. The device provides the measurement value immediately after 2 minutes.
The normal values for eNO are between 10 - 30 ppb. Elevated values > 30 ppb indicate eosinophilic inflammation in the airways.
We recently demonstrated that all patients with an elevated eNO value > 46 ppb showed severe obstruction during cold airflow stress (Dressler et al 2019). Figuratively speaking, one can say that an elevated eNO can be seen as “rust” in the lungs. If anti-inflammatory therapy with inhaled steroids (ICS) is started, a rapid decline in NO levels can be seen within 2 weeks, making eNO a good parameter for the response to therapy in bronchial asthma.
Pulmonary function test
Depending on age, lung function is tested using oscilloresistometry, spirometry or bodyplethsymography. The examinations begin with detailed instructions for children and adults. The examination procedure is described and demonstrated. A nose clip closes both nostrils and the mouthpiece should be firmly enclosed with the lips. With small children, at least one parent should be present for each measurement.
The following values are measured during spirometry: Vital capacity = VC (L /%)
Forced vital capacity = FVC (L / %), FEV1 (L / %) Tiffeneau Index (FEV1/VC)
The reserve volume (RV) can only be determined using body plethysmography. Spirometry is used to differentiate between obstructive (Fig. 4a), restrictive (Fig. 4b) and combined obstructive and restrictive ventilation disorders.
Measurement of lung function with oscilloresistometry
In oscilloresistometry, the airways are examined using sound waves. High frequencies (20 Hz) penetrate less deeply into the airways than low frequencies (5 Hz). Pulse oscillometry essentially consists of a loudspeaker (A), a pneumotachograph (B), a mouthpiece with filter (C) and a transducer (D) (Fig. 5).
Advantages of oscilloresistometry:
- Resting respiration analysis (cooperation independent)
- Children from the age of 3 can be measured.
- Differentiation between central and peripheral airways
- Helps to better interpret spirometry
The normal values for eNO are between 10 - 30 ppb. Elevated values > 30 ppb indicate eosinophilic inflammation in the airways.
We recently demonstrated that all patients with an elevated eNO value > 46 ppb showed severe obstruction during cold airflow stress (Dressler et al 2019). Figuratively speaking, one can say that an elevated eNO can be seen as “rust” in the lungs. If anti-inflammatory therapy with inhaled steroids (ICS) is started, a rapid decline in NO levels can be seen within 2 weeks, making eNO a good parameter for the response to therapy in bronchial asthma.
Measurement of lung function with body plethysmography
Body plethysmography or whole-body plethysmography is often referred to as “major lung function”. The measurement with body plethysmography is the ideal lung function test method, as it can calculate the specific airway resistance including the breathing loop, the thoracic gas volume and all the parameters that can be derived from it in addition to the measured variables of spirometry. The body plethysmograph is carried out in a cabin with a (largely) closed air volume and looks like a small telephone booth (Fig. 6).
The maximum vital capacity (VCmax), the forced vital capacity (FVC), the airway resistance (R), the one-second capacity (FEV1), the Tiffeneau index (FEV1/VC), the maximum expiratory flow at 25% of the forced vital capacity (MEF25), the total lung volume (TGV), the residual volume (RV) and the functional residual capacity (RV/TLC) are measured.
Body plethysmography or whole-body plethysmography is often referred to as “major lung function”. The measurement with body plethysmography is the ideal lung function test method, as it can calculate the specific airway resistance including the breathing loop, the thoracic gas volume and all the parameters that can be derived from it in addition to the measured variables of spirometry. The body plethysmograph is carried out in a cabin with a (largely) closed air volume and looks like a small telephone booth (Fig. 6).
The maximum vital capacity (VCmax), the forced vital capacity (FVC), the airway resistance (R), the one-second capacity (FEV1), the Tiffeneau index (FEV1/VC), the maximum expiratory flow at 25% of the forced vital capacity (MEF25), the total lung volume (TGV), the residual volume (RV) and the functional residual capacity (RV/TLC) are measured.
Measurement of bronchial reversibility
In accordance with the international and national care guidelines (GINA and NVL Asthma), bronchial reversibility or the bronchial dilatation test is carried out as an important diagnostic criterion for the diagnosis of asthma. If your doctor determines that your lung function or FEV1 is restricted according to normal values, they will give you 4 doses = 400 mg of a bronchodilator, salbutamol, to inhale.
An increase in FEV1 of 12 % and 200 ml following salbutamol inhalation indicates a positive reversibility test and the diagnosis of asthma can be confirmed.
Measurement of bronchial sensitivity
In many cases, the lung function of patients with asthma is completely normal at rest. This is particularly true in children and adolescents who do not yet have chronic changes in lung function. In this case, bronchial sensitivity is measured using methacholine, for example. Methacholine is an active substance from the group of muscarinic receptor agonists, which triggers a narrowing of the bronchi (obstruction) in sensitive bronchi.
A mean methacholine concentration (16 mg/dl) is used, from which it is known that healthy people react only slightly, if at all, with an increase in airflow resistance and a corresponding drop in FEVq1. The extent of the drop in FEV1 by 20% (PD20 FEV1) is the measure of bronchial sensitivity.
The solution is nebulized via an aerosol provocation system (Viasys Healthcare GmbH, Höchberg) and applied bronchially to the patient via a trigger mechanism during the inspiratory phase. For the provocation study, we used the following protocol with five stages (table), which provided for up to five dose applications. Starting with 0.01 mg methacholine, four stages followed with 0.1 mg, 0.4 mg, 0.8 mg and 1.6 mg.
If there is a positive reaction during the methacholine test, you may feel a slight tightness in your chest and you may experience wheezing and coughing. These symptoms are short-term and can be reversed immediately by inhaling salbutamol.
Typically, patients with asthma have a high-grade BHR < 0.1 mg methacholine.
| Stage | Step Dose Methacholine [mg] | Cumulative Dose [mg] | Assessment / Interpretation |
|---|---|---|---|
| 1 | 0.01 | < 0.1 mg | Severe BHR |
| 2 | 0.10 | 0.1 – < 0.3 mg | Moderate BHR |
| 3 | 0.40 | 0.3 – < 0.6 mg | Mild BHR |
| 4 | 0.80 | < 0.6 – 1.0 mg | Borderline |
| 5 | 1.60 | > 1 mg | No BHR |
Nasal and bronchial allergen provocation
Nasal allergen provocation examines whether the nasal symptoms (sneezing, runny nose) are actually caused by the specific allergen. Before the allergen is administered, the control solution (isotonic saline solution) is first sprayed into the nose. (Fig. 1). 15 minutes later, the allergen to be tested (e.g. house dust mite, birch or mold) is sprayed into the nose. The symptoms (such as sneezing, itching, watery eyes, runny nose and nasal obstruction) are then observed and documented according to Lebel over the next 10 minutes. An increase in the Lebel score by 5 points is clearly positive. The nasal provocation test is considered safe, but is only meaningful in experienced hands.
The clinical relevance of an allergen cannot always be proven by the skin test or the determination of the specific IgE in the blood and the typical clinic (symptoms after allergen contact). In some cases, the doctor recommends carrying out a provocation test before initiating specific immunotherapy in order to prove the relevance of the allergen to the asthma.
During this test, you will inhale a standardized allergen (e.g. house dust mites) in ascending doses at short intervals via the aerosol provocation system (Viasys Healthcare GmbH, Höchberg) (Fig. 7). Your lung function is checked at the beginning, during the test and afterwards.
When measuring the bronchial allergen load, a slight spasm of the airways may occur (determination of the bronchial irritation threshold for the allergen). This can lead to a short-term early reaction (in the period from 10 minutes to 3 hours after allergen inhalation) with a slight drop in lung function and sometimes a cough and wheezing may occur. If this reaction occurs, the doctor will give you salbutamol to inhale, which will reverse this effect.
After allergen inhalation, however, a late reaction (in the period of 6 to 9 hours after allergen inhalation) can also occur. For this reason, lung function should be monitored and measured every hour. If there is a late reaction with a significant narrowing of the airways, salbutamol is inhaled again. In the event of severe airway constriction, 50 mg prednisone is taken as a precaution.
Oral food provocation test
A positive IgE antibody test in the blood or a skin test does not provide any information about the severity of a possible allergic reaction of the immune system. To check this, food provocation is necessary in many cases.
Oral food provocation is an established procedure in which a food to which you may be allergic is ingested in increasing amounts under medical supervision to diagnose or rule out a food allergy.
During food provocation, you could theoretically experience an allergic reaction. Typically, you may experience itching in the throat, swelling of the lips and individual itchy wheals. If the doctor identifies these initial symptoms together with you, the food challenge will be discontinued. If necessary, the allergic reactions are then treated with medication (anti-histamines, cortisone, etc.).
The food provocation is standardized for peanuts
1 mg (equivalent to 1/1000 of a peanut), 3 mg (equivalent to 1/3000 of a peanut), 10 mg (1/100 of a peanut), 30 mg (3/100 of a peanut), 100 mg (1/10 of a peanut), and 300 mg (3/10 of a peanut) of peanut protein or an appropriate placebo are tested.
Laboratory investigations
Additionally, in collaboration with colleagues from other specialties, radiological examinations such as computed tomography (CT), magnetic resonance imaging (MRI), or specific laboratory tests can be performed.
Schedule an appointment
Schedule your appointment with Prof. Dr. Zielen online
