Asthma laboratory findings: Difference between revisions
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*A markedly elevated [[eosinophil|serum eosinophil count]] greater than 15% may suggest an underlying allergic disease. | *A markedly elevated [[eosinophil|serum eosinophil count]] greater than 15% may suggest an underlying allergic disease. | ||
*[[Charcot-Leyden crystals]] are microscopic [[eosinophil|eosinophilic lysophospholipase]] | *[[Charcot-Leyden crystals|Charcot-leyden crystals]] are microscopic [[eosinophil|eosinophilic lysophospholipase]] that are present in the [[sputum]] and are indicative of an [[eosinophil|eosinophilic inflammation or proliferation]], such as found in allergic reactions. [[Curschmann's Spirals|Curschmann's spirals]] are mucus casts that may also be seen in the distal airways. | ||
*Measurement of [[Eosinophil|sputum eosinophil count]] has shown to predict the response to [[corticosteroid|steroid therapy]] and also help to monitor the airway inflammation.<ref name="pmid16537853">Bacci E, Cianchetti S, Bartoli M, Dente FL, Di Franco A, Vagaggini B et al. (2006) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=16537853 Low sputum eosinophils predict the lack of response to beclomethasone in symptomatic asthmatic patients.] ''Chest'' 129 (3):565-72. [http://dx.doi.org/10.1378/chest.129.3.565 DOI:10.1378/chest.129.3.565] PMID: [http://pubmed.gov/16537853 16537853]</ref><ref>doi:10.1378/chest.129.3.503CHEST March 2006 vol. 129 no. 3 503-504 [http://chestjournal.chestpubs.org/content/129/3/503.full]</ref> A small controlled prospective study demonstrated a significant symptomatic benefit with the use of steroid to control sputum eosinophilia. Thereby, suggested '''normalisation of the induced sputum eosinophil count''' to reduce the incidence of asthma exacerbations and admissions and also reduced the need for additional anti-inflammatory therapy.<ref name="pmid12480423">Green RH, Brightling CE, McKenna S, Hargadon B, Parker D, Bradding P et al. (2002) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=12480423 Asthma exacerbations and sputum eosinophil counts: a randomised controlled trial.] ''Lancet'' 360 (9347):1715-21. [http://dx.doi.org/10.1016/S0140-6736(02)11679-5 DOI:10.1016/S0140-6736(02)11679-5] PMID: [http://pubmed.gov/12480423 12480423]</ref> | *Measurement of [[Eosinophil|sputum eosinophil count]] has shown to predict the response to [[corticosteroid|steroid therapy]] and also help to monitor the airway inflammation.<ref name="pmid16537853">Bacci E, Cianchetti S, Bartoli M, Dente FL, Di Franco A, Vagaggini B et al. (2006) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=16537853 Low sputum eosinophils predict the lack of response to beclomethasone in symptomatic asthmatic patients.] ''Chest'' 129 (3):565-72. [http://dx.doi.org/10.1378/chest.129.3.565 DOI:10.1378/chest.129.3.565] PMID: [http://pubmed.gov/16537853 16537853]</ref><ref>doi:10.1378/chest.129.3.503CHEST March 2006 vol. 129 no. 3 503-504 [http://chestjournal.chestpubs.org/content/129/3/503.full]</ref> A small controlled prospective study demonstrated a significant symptomatic benefit with the use of steroid to control sputum eosinophilia. Thereby, suggested '''normalisation of the induced sputum eosinophil count''' to reduce the incidence of asthma exacerbations and admissions and also reduced the need for additional anti-inflammatory therapy.<ref name="pmid12480423">Green RH, Brightling CE, McKenna S, Hargadon B, Parker D, Bradding P et al. (2002) [http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=12480423 Asthma exacerbations and sputum eosinophil counts: a randomised controlled trial.] ''Lancet'' 360 (9347):1715-21. [http://dx.doi.org/10.1016/S0140-6736(02)11679-5 DOI:10.1016/S0140-6736(02)11679-5] PMID: [http://pubmed.gov/12480423 12480423]</ref> | ||
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*Pulse oximetry may be useful to exclude [[hypoxemia]], particularly in uncomplicated cases, wherein administration of oxygen is useful to eliminate hypoxemia. | *Pulse oximetry may be useful to exclude [[hypoxemia]], particularly in uncomplicated cases, wherein administration of oxygen is useful to eliminate hypoxemia. | ||
==Allergy Testing== | |||
The two most commonly used tests to assess the allergic sensitivity to specific envirnomental allergens include allergic skin testing and measurement of [[IgE|serum IgE]] levels. | |||
====Serum IgE==== | |||
*A normal '''total serum IgE''' level does not exclude the diagnosis of asthma; however in a patient with recurrent episodes secondary to [[allergen|allergen exposure]], may report positive for allergic tests and is associated with a higher positive predictive value. A total serum IgE level of greater than 100 IU/mL is characteristic of underlying allergic disease; however, levels greater than 1000 IU/mL is highly suggestive of [[eczema]] or [[allergic bronchopulmonary aspergillosis]]. | |||
*'''Allergen-specific IgE''' using immuno-fluorescence is most commonly employed to identify specific envirnomental allergens and have replaced radio-allergo-sorbent tests (RAST). | |||
====Allergy Skin Test==== | |||
*Skin testing is another method that may be used to assess the allergic sensitivity to specific aero-allergens such as dust, pollen and mold spores. | |||
*Asthmatics and patients with associated [[allergic rhinitis]] may benefit from allergy immunotherapy. | |||
==References== | ==References== | ||
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[[Category:Emergency medicine]] | [[Category:Emergency medicine]] | ||
[[Category:Intensive care medicine]] | [[Category:Intensive care medicine]] | ||
[[Category:Up-To-Date]] | |||
{{WH}} | {{WH}} | ||
{{WS}} | {{WS}} |
Revision as of 01:11, 22 September 2011
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Asthma laboratory findings On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S. [3]
Overview
Routine laboratory tests are not indicated for the diagnosis of asthma but may be used to exclude other causes of wheeze. Elevated eosinophil count and elevated serum IgE levels may be observed in patients with a repeated history of allergic trigger. Arterial blood gas and pulse oximetry may be used to assess the disease severity and response to therapy.
Serum and Sputum Examination
- A markedly elevated serum eosinophil count greater than 15% may suggest an underlying allergic disease.
- Charcot-leyden crystals are microscopic eosinophilic lysophospholipase that are present in the sputum and are indicative of an eosinophilic inflammation or proliferation, such as found in allergic reactions. Curschmann's spirals are mucus casts that may also be seen in the distal airways.
- Measurement of sputum eosinophil count has shown to predict the response to steroid therapy and also help to monitor the airway inflammation.[1][2] A small controlled prospective study demonstrated a significant symptomatic benefit with the use of steroid to control sputum eosinophilia. Thereby, suggested normalisation of the induced sputum eosinophil count to reduce the incidence of asthma exacerbations and admissions and also reduced the need for additional anti-inflammatory therapy.[3]
Arterial Blood Gas
- Arterial blood-gas is used to evaluate the respiratory function and may be reserved to patients with severe acute exacerbation of asthma at which point ABG may reveal respiratory alkalosis that is consistent with the hypoxemia and/or hypercarbia secondary to significant hypoventilation.
- Hypercarbia in particular is an important indicator of hypoventilation, that may be used to decide the need for mechanical ventilation, in cases of markedly elevated PCO2.
Pulse Oximetry
- Measurement of oxygen saturation by pulse oximetry may be useful to identify patients with acute severe asthma who may rapidly progress to respiratory failure and thereby require more intensive therapy.[4]
- Pulse oximetry may be useful to exclude hypoxemia, particularly in uncomplicated cases, wherein administration of oxygen is useful to eliminate hypoxemia.
Allergy Testing
The two most commonly used tests to assess the allergic sensitivity to specific envirnomental allergens include allergic skin testing and measurement of serum IgE levels.
Serum IgE
- A normal total serum IgE level does not exclude the diagnosis of asthma; however in a patient with recurrent episodes secondary to allergen exposure, may report positive for allergic tests and is associated with a higher positive predictive value. A total serum IgE level of greater than 100 IU/mL is characteristic of underlying allergic disease; however, levels greater than 1000 IU/mL is highly suggestive of eczema or allergic bronchopulmonary aspergillosis.
- Allergen-specific IgE using immuno-fluorescence is most commonly employed to identify specific envirnomental allergens and have replaced radio-allergo-sorbent tests (RAST).
Allergy Skin Test
- Skin testing is another method that may be used to assess the allergic sensitivity to specific aero-allergens such as dust, pollen and mold spores.
- Asthmatics and patients with associated allergic rhinitis may benefit from allergy immunotherapy.
References
- ↑ Bacci E, Cianchetti S, Bartoli M, Dente FL, Di Franco A, Vagaggini B et al. (2006) Low sputum eosinophils predict the lack of response to beclomethasone in symptomatic asthmatic patients. Chest 129 (3):565-72. DOI:10.1378/chest.129.3.565 PMID: 16537853
- ↑ doi:10.1378/chest.129.3.503CHEST March 2006 vol. 129 no. 3 503-504 [1]
- ↑ Green RH, Brightling CE, McKenna S, Hargadon B, Parker D, Bradding P et al. (2002) Asthma exacerbations and sputum eosinophil counts: a randomised controlled trial. Lancet 360 (9347):1715-21. DOI:10.1016/S0140-6736(02)11679-5 PMID: 12480423
- ↑ Overall JE (1975) Rating session. Video taped interviews and BPRS ratings. Psychopharmacol Bull 11 (1):15. PMID: 1121560