Exogenous allergic alveolitis - Diagnosis

Laboratory data

General blood test - changes depend on the clinical form of the disease, the activity of the process.

The acute form of exogenous allergic alveolitis is characterized by leukocytosis, a shift in the leukocyte formula to the left, moderate eosinophilia (an inconstant sign), and an increase in ESR. In exogenous allergic alveolitis caused by aspergilli, significant eosinophilia may be observed.

Similar changes in the hemogram are observed in the subacute form of the disease, but may be less pronounced.

In the chronic form of exogenous allergic alveolitis, symptomatic erythrocytosis may develop and the hemoglobin level may increase (with progressive respiratory failure), the number of leukocytes and ESR may increase during the period of exacerbation of the disease, in the remission phase - the number of leukocytes may remain normal.

Biochemical blood test - with pronounced activity of the disease (primarily in acute and subacute forms), an increase in the content of gamma globulins, seromucoid, haptoglobin, and sialic acids is observed.

General urine analysis - no significant changes.

Immunological studies - a possible decrease in the subpopulation of T-lymphocyte suppressors, positive reactions of lymphocyte blast transformation (LBTL) and inhibition of leukocyte migration with a specific antigen are observed, detection of circulating immune complexes is possible.

Specific IgG antibodies are also detected using the Ouchterlony precipitation reaction, passive hemagglutination, counter immunoelectrophoresis, enzyme immunoassay, and laser nephelometry. However, it should be noted that specific antibodies to the antigen are not always detected in the blood and their absence does not contradict the diagnosis of exogenous allergic alveolitis in the presence of other characteristic signs of the disease.

Often, the basophil degranulation and leukolysis test is positive in the presence of the allergen that causes the disease.

Study of fluid obtained during bronchial lavage - during the period of exacerbation of the disease, an increase in the number of neutrophils and lymphocytes, a decrease in the number of T-lymphocytes-suppressors is observed; as the process subsides, the number of T-lymphocytes-suppressors increases. An increase in the content of IgA, G, M is also characteristic.

Instrumental research

X-ray of the lungs

The acute form of exogenous allergic alveolitis is manifested by widespread interstitial changes in the lungs in the form of reticulation, blurred contours of the vessels, and possible infiltrative changes with blurred contours located in the lower parts of both lungs and subpleurally.

In the subacute form of exogenous allergic alveolitis, bilateral small focal darkenings of 0.2-0.3 cm in diameter (reflection of the granulomatous process in the lungs) are detected. After the cessation of the effect of the etiologic factor, these changes in the lungs gradually disappear within 1-2 months. With continued contact with the allergen, already in the subacute stage, pronounced signs of interstitial fibrosis appear.

In the chronic form of exogenous allergic alveolitis, characteristic signs of severe pulmonary fibrosis are revealed: widespread cellular deformation of the pulmonary pattern, diffuse reticular and linear shadows, a “honeycomb lung” pattern, signs of lung wrinkling, and pulmonary hypertension.

Study of external respiratory function

In the acute phase of exogenous allergic alveolitis, a decrease in VC is detected and moderate impairment of bronchial patency is noted (due to the development of bronchioloalveolitis). Similar changes are also recorded in the subacute phase of the disease. In the chronic form of exogenous allergic alveolitis, a restrictive type of respiratory failure is formed, characterized by a sharp decrease in VC.

Blood gas analysis

Blood gas composition disorders are observed mainly in patients with chronic exogenous allergic alveolitis as interstitial fibrosis progresses and severe respiratory failure develops. At this stage of the disease, the diffusion capacity of the lungs is sharply impaired, and arterial glycosemia develops.

ECG. It is possible to detect deviations of the electrical axis of the heart to the right; with pronounced clinical manifestations and a long course of exogenous allergic alveolitis, ECG signs of myocardial hypertrophy of the right atrium and right ventricle appear.

Lung tissue biopsy

Transbronchial and open lung biopsy are used. In the development of the chronic form of exogenous allergic alveolitis, open biopsy is used, since percutaneous biopsy is uninformative. The main morphological signs of exogenous allergic alveolitis in lung biopsy are:

• lymphocytic infiltration of the alveoli and interalveolar septa;
• the presence of granulomas (not detected in chronic forms of the disease);
• signs of alveolar obliteration;
• interstitial fibrosis with deformation of the bronchioles;
• areas of pulmonary emphysema, fragmentation and reduction in the number of elastic fibers;
• detection of immune complexes in the walls of the alveoli (using the immunofluorescence method of studying the biopsy).

Diagnostic criteria for exogenous allergic alveolitis

The diagnosis of exogenous allergic alveolitis can be made on the basis of the following provisions:

• the presence of a connection between the development of a disease and a specific etiological factor;
• disappearance in most cases of disease symptoms or their significant reduction after cessation of contact with the allergen;
• positive results of provocative inhalation tests under natural (industrial) conditions. The patient is examined before starting work, then in the middle and at the end of the working day. The following parameters are assessed: respiratory rate, body temperature, vital capacity, general well-being of the patient. Usually, before starting work, these parameters are at the lower limit of the norm or reduced, the patient's condition is satisfactory. In the middle and, especially, at the end of the working day, all parameters and the general condition of the patient undergo very
  pronounced negative dynamics due to the influence of industrial etiological factors during the day. The test is highly specific and is not accompanied by complications. There is also a unique acute inhalation test. The patient is asked to inhale an aerosol containing the suspected antigens and assess the above parameters. If the patient has exogenous allergic alveolitis, these parameters and the patient's well-being deteriorate sharply. It should be noted that the named diagnostic tests are most informative in acute and subacute exogenous allergic alveolitis and are much less informative in chronic forms;
• positive intradermal tests with an allergen that is suspected of causing exogenous allergic alveolitis;
• detection of specific precipitating antibodies in the blood;
• bilateral widespread crepitation, more pronounced over the basal parts of the lungs;
• X-ray picture of pulmonary dissemination of a nodular nature or diffuse interstitial changes and “honeycomb” lung;
• restrictive type of ventilation disorders in a functional study of the lungs in the absence or minor disorders of bronchial patency;
• detection of specific stimulation of lymphocytes in RBTL (lymphocyte blast transformation reaction) or RTML (leukocyte migration inhibition reaction);
• characteristic morphological manifestations in lung biopsies.

Differential diagnosis

Differential diagnosis of exogenous allergic alveolitis should be carried out with other forms of fibrosing alveolitis, primarily with idiopathic fibrosing alveolitis.

It is often necessary to differentiate exogenous allergic alveolitis from bronchial asthma. Unlike exogenous allergic alveolitis, bronchial asthma is characterized by:

• attacks of suffocation, during which a large number of dry whistling and buzzing rales are heard;
• disappearance of dry wheezing during the interictal period;
• obstructive type of pulmonary ventilation disorders;
• high levels of IgE in the blood of patients;
• determination of eosinophils, Charcot-Leyden crystals, and Curschmann spirals in the sputum of patients.

In the differential diagnosis of exogenous allergic alveolitis with chronic obstructive bronchitis, it should be taken into account that, unlike exogenous allergic alveolitis, chronic obstructive bronchitis is characterized by:

• long-term smoking over many years;
• scattered dry whistling and buzzing rales during auscultation of the lungs;
• obstructive type of pulmonary ventilation dysfunction;
• a hacking cough with the separation of mucopurulent sputum;
• positive effect of treatment with bronchodilators-anticholinergics (ipratropium bromide), beta2-adrenergic receptor stimulants.

Survey program

1. General blood and urine tests.
2. Biochemical blood test: determination of total protein and protein fractions, haptoglobin, seromucoid, aminotransferases, bilirubin, creatinine, urea.
3. Immunological studies: determination of the content of T- and B-lymphocytes, subpopulations of T-lymphocytes, immunoglobulins, circulating immune complexes, RBTL and RTML with the putative allergen - the etiological factor of the disease.
4. Inhalation challenge test in industrial conditions or acute inhalation test.
5. ECG.
6. X-ray of the lungs.
7. Spirometry.
8. Determination of blood gas composition.
9. Study of bronchial lavage fluid: determination of the cellular composition of T- and B-lymphocytes, subpopulations of T-lymphocytes, immunoglobulins.
10. Open lung biopsy.

Examples of diagnosis formulation

1. Exogenous allergic alveolitis ("farmer's lung"), acute form.
2. Exogenous allergic alveolitis ("bird breeder's lung"), chronic form. Chronic non-obstructive bronchitis. Respiratory failure stage II. Chronic compensated pulmonary heart disease.

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