Role of clinical laboratory in allergy testing

Clients and clinician satisfaction with laboratory services at selected government hospitals in eastern Ethiopia

Background

In clinical laboratory service, patients and clinical service providers are the primary focus of survey of satisfaction in many countries. The objective of the study was to assess clients’ and clinicians’ satisfaction with laboratory services at selected government hospitals in eastern Ethiopia from May to June, 2010.

Findings

A cross sectional study was conducted at Dil Chora, Jugal, Hiwot Fana and Bisidimo hospitals. Data were collected from 429 patients and 54 clinical service providers. A statistical analysis was conducted using Likert Scale and SPSS Version 16 software. Most of the patients (87.6%) were satisfied with the laboratory services. The lowest [2.48 ± 1.39] and highest [4.27 ± 0.83] rate satisfaction were on cleanness of latrine to collect specimens and availability of laboratory staff on working hours respectively. The extent of the patients’ satisfaction was different among the study hospitals (P-value < 0.05). Most of the clinical services providers (80%) were also satisfied with the laboratory services. The lowest [3.02 ± 1.36] and highest [3.78 ± 1.03] rate of satisfaction were found on critical value notification and timely test results for HIV/AIDS patients care respectively.

Conclusion

The overall degree of customers’ satisfaction with laboratory services was high. But there were some services such as the cleanness of latrines, information given during specimen collection outside laboratory and critical value notification which need attention. Therefore, the hospital administrations and the laboratory departments should work harder and closely to solve the identified problems. Further study with a larger sample size and more factors is recommended.

Surface plasmon resonance immunosensor for histamine based on an indirect competitive immunoreaction

The use of a surface plasmon resonance immunosensor for the analysis of histamine (beta-imidazole ethylamine) is described. The method is based on an indirect competitive reaction of an anti-histamine antibody in a sample solution with histamine immobilized on a sensor chip and with histamine in the sample solution. A sensor chip immobilized with histamine was prepared using a self-assembly monolayer of 11-mercaptoundecanoic acid (11-MUA) as an anchor membrane, followed by an amino-coupling reaction with histamine after activation of the 11-MUA layer on the sensor chip by treatment with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide. The sensor chip can be reused, after regeneration with a 10mM HCl solution, which dissociates the anti-histamine antibody complex from histamine on the sensor chip. The affinity constants for the immunocomplex of the anti-histamine antibody with histamine in the solution and for that of the anti-histamine antibody with histamine immobilized on the sensor chip were calculated to be 1.5 x 10(7) and 7.2 x 10(5) M(-1), respectively, by assuming a Langmuir-type adsorption of the anti-histamine antibody to histamine immobilized on the sensor chip. The detection limit of the method was determined to be 3ppb.

Current in vivo and in vitro screens for inhalant allergy

Screening for inhalant allergy requires the use of a rapid, accurate, cost-effective methodology for the detection of the presence or absence of allergic responsiveness. In vivo and in vitro methods have been demonstrated to be sensitive and specific in the diagnosis of inhalant allergy, even with panels as small as seven or eight antigens. There is good concurrence between skin testing techniques and various serum measures of specific IgE, and both methods can be used effectively for screening inhalant allergy, although per-test costs for in vitro methods remain higher than comparable costs for skin testing [28]. Although the rapidity of both methods is acceptable, skin testing allows immediate observation and interpretation of test results, whereas all in vitro methods involve serum processing that delays results for hours to days. In general, both in vitro methods and epicutaneous testing with a device such as the Multi-Test II offer the clinician effective techniques in screening for inhalant allergy. Each technique has benefit and can be used in both primary care practices and in specialists' offices. The choice of the primary technique to be used for screening depends on the type of practice, the practice's familiarity with skin testing, the geographic region, and the relevant payer mix. A review of the relevant research on allergy screening suggests that the number of antigens used should be in the range of 8 to 12 and should include representative allergens from all the significant classes for the specific geographic [table: see text] region. This screen would probably contain one or two grasses, weeds, and trees, two or three molds, cat allergen, and one dust mite allergen. A sample panel is demonstrated in Box 6. It is important to recognize that the diagnosis and treatment of inhalant allergy is a fluid process. In patients who have negative allergy screens but for whom suspicion of inhalant allergy remains high, additional testing with ID techniques is sometimes indicated. This procedure might be suggested in patients for whom there is a high suspicion of mold allergy or who have unusual inhalant exposures. These individuals may represent a failure of the screening process and require additional testing. In these unusual cases, the judgment of the otolaryngic allergist is critical in guiding this further diagnostic work-up. The use of screening procedures for the diagnosis of inhalant allergy provides a rapid, accurate, and cost-effective method for evaluating patients with a history suggestive of allergic disease. Research suggests that a screening panel has strong clinometric properties and has both sensitivity and specificity in excess of 95%. It is statistically unlikely that a patient with negative findings to an allergy screen will demonstrate clinically significant inhalant allergy.

Clinical value and measurement of specific IgE

The diagnosis of human allergic diseases involves the combined use of a careful clinical history, physical examination, and in vitro and in vivo assay methods for the detection of IgE antibodies of defined allergen specificities. In vivo (skin testing) and in vitro (measurement of specific IgE in serum) techniques cannot be considered interchangeable, the former reflecting not only the presence of IgE but also mast cell integrity, vascular and neural responsiveness. Both techniques have similarities and differences, advantages and disadvantages. Recently introduced "second generation" immunoassays have continued to improve the analytical sensitivity and reproducibility thanks to automation and improved reagent quality. Quantitative assays may allow the use of specific clinical thresholds able to differentiate symptomatic from asymptomatic patients. False-negative and false-positive results should derive from lability of some major extracts, and from possible cross-reactivities, respectively. Characterization of allergens at a molecular and submolecular level and, where necessary, the use of recombinant allergens can reduce cross-reactions and further improve the quality of immunoassays.

Brown Norway rat ovalbumin-specific immunoglobulin E antibodies increase the human basophil expression of CD63 marker

Anaphylactic shock is an immunoglobulin E (IgE)-dependent hypersensitivity. Biological tests like leucocyte histamine release (LHR) and human basophil activation (HBA), frequently used in human allergy, reflect both the amount of IgE fixed on cells and the cellular reactivity. To assess whether serum-specific IgE from Brown Norway (BN) rats prepared for ovalbumin (OVA)-induced anaphylactic shocks can activate human basophils which has a potential interest in experimental allergy: such a test could rapidly assert an IgE sensitization in laboratory animals genetically T-helper 2 (Th2)-predisposed. Rats (n = 39) were immunized three times (day 0, day 5 and day 21) with OVA injected subcutaneously. One week after the third immunization, a shock was induced with an intravenous (i.v.) bolus of OVA. Sensitization was assessed by passive cutaneous anaphylaxis (PCA) test and dosages of serum IgE antibodies anti-OVA by enzyme-linked immunosorbent assay. Blood basophils were counted before and during the shock. Before the shock induction (at day 21), an LHR test was performed on rat blood, and human basophils were sensitized with rat sera. HBA was demonstrated by the increase in the percentage of cells expressing CD63 antigen membrane, measured by flow cytometry. Twenty-one days after the first subcutaneous (s.c.) immunization, the rat serum induced a significant HBA. HBA was observed neither with the same serum previously heated nor with the serum from nonimmunized rats (NIRs). OVA-specific IgEs were significantly increased in immunized rat (IR) serum. The PCA test was negative when the serum was previously heated (56 degrees C). We never observed any circulating basophils, and LHR test was negative. After OVA i.v. administration, all IRs died rapidly. HBA testing strongly suggests a mediation by specific IgE in the increase of CD63 in BN rats. Thus, HBA test seems useful in assessing whether an experimental allergy was induced in animals genetically predisposed to an immune response, Th2-mediated, like BN rat. We also conclude that rat basophil activation does not participate in the histamine release during anaphylactic shock in sensitized BN rats.

Marked improvement of the basophil activation test by detecting CD203c instead of CD63

BACKGROUND

The flow cytometric basophil activation test by detection of CD63 expression has been developed as an alternative method for in vitro diagnosis of IgE-mediated reactions to various allergens. Despite promising initial studies, the test remains disappointing in terms of sensitivity. CD203c has recently been demonstrated as a specific activation marker of basophils that is rapidly up-regulated after allergen challenge in sensitized patients.

OBJECTIVE

The goal of the present study was to compare basophil activation tests by using either CD203c or CD63 in the diagnosis of immediate-type allergy to latex.

METHODS

Twenty-seven patients (health care workers of our institution) who developed clinical features evocative of allergy after contact with latex were included and classified into two groups. Group 1 (n = 16) comprised true allergic patients who presented with typical signs of immediate allergic reaction associated with a positive skin test (prick test). Group 2 (n = 11) consisted of patients whose clinical history was not typical and had negative skin test. Twelve healthy subjects were also studied as controls. We compared the sensitivity of two triple-staining flow cytometric protocols measuring basophil activation after latex stimulation: CD45-IgE-CD63 and CD45-IgE-CD203c.

RESULTS

The CD203c protocol showed a higher sensitivity than the CD63 protocol (75% vs. 50%). In comparison, latex-specific IgE sensitivity was found to be 69%. Furthermore, the magnitude of the basophil response was significantly higher with CD203c in comparison with CD63. Specificity was 100% for both protocols.

CONCLUSION

Due to superior gating of basophils and a higher range of activation in response to allergen, the basophil activation test is markedly improved by use of CD203c instead of CD63.

The Po River Delta epidemiological survey: reference values of total serum IgE levels in a normal population sample of North Italy (8-78 yrs)

The aim of this paper was to define, for the first time in Italy, normal levels of total serum IgE in a general population sample of North Italy. Total serum IgE in 1905 subjects, living in Po Delta area (near Venice), were measured by PRIST method. Normal values were derived from 558 subjects without asthma and/or asthmatic/rhinitic symptoms, noncurrent smokers, skin prick-test negatives ('normals'). Cut-off values to differentiate 'normals' from the remaining part of the sample ('others'), from asthmatic, and from rhinitic subjects, were established with the IgE value midway between the upper limit of the 95% confidence intervals (CI) of the geometric mean for 'normals' and the lower limit for 'others', asthmatics, and rhinitics, respectively. Geometric mean of normal children-adolescents was 45 kU/L (SD: 2.6; 95% CI: 38-63). In normal adults geometric mean was 29 kU/L (SD: 3.3; 95% CI: 25-40) in males and 19 kU/L (SD: 3.8; 95% CI: 16-22) in females. The diagnostic sensitivity of IgE test was low, while the specificity was very high. A good positive predictive value in discriminating 'normals' from 'others' was found, on the contrary, we found a good negative predictive value in discriminating 'normals' from asthmatics or from rhinitics. In conclusion, our results confirm that it is necessary to provide separate total serum IgE reference values for what concerns age in children-adolescents and in adults, and gender, in adults. Low serum IgE are helpful to exclude allergic asthma or rhinitis level of total.

Monitoring of basophil activation using CD63 and CCR3 in allergy to muscle relaxant drugs

Allergic or pseudoallergic reactions that occur during anesthesia have been increasing for the last few years. To date, the diagnosis of allergy to muscle relaxants remains difficult. In this respect, we developed a flow cytometric method for the study of drug-induced basophil degranulation using CD63 and CCR3. Fifty patients who developed clinical features evocative of allergic reactions immediately after induction of anesthesia were included and classified into two groups. Group 1 (n = 39) comprised true allergic patients, who developed typical signs of shock associated to positive skin testing. Group 2 (n = 11) consisted of patients whose clinical history was not typical and skin testing was negative or nonconclusive. Seventeen control subjects were also studied in this report. We compared data from flow cytometry to skin tests, specific IgE, and histamine release results. Flow cytometry showed a sensitivity of 54%, while that of specific IgE was similar, at 62%. Interestingly, when considering the sensitivity of IgE + CD63 for diagnosis, we reached a sensitivity value of 80%. Of 15 negative results for specific IgE, we found 7 positive CD63 tests, while histamine release gave positive results in only 2 cases. Furthermore, the CD63 protocol showed good specificity (100%). We conclude that our flow cytometry protocol is a promising tool in allergy diagnosis since it is specific and complementary to specific IgE detection.

Specific IgE to cross-reactive carbohydrate determinants strongly affect the in vitro diagnosis of allergic diseases

BACKGROUND

Cross-reacting carbohydrate determinants (CCDs) are antigenic structures shared by allergenic components from taxonomically distant sources. The case history of a patient with a great discrepancy between skin test and specific IgE results led us to investigate the role of these determinants in his specific case and in an allergic population.

OBJECTIVE

We sought to determine the role of CCDs in causing false-positive and clinically irrelevant results in in vitro tests.

METHODS

The involvement of CCDs was studied by specific IgE inhibition by using glycoproteins with a known carbohydrate structure. Direct and inhibition assays were performed by commercially available systems, in-house ELISA, and the immunoblotting technique. The binding to the periodate-oxidated carbohydrate structure of glycoproteins and allergenic extracts was also evaluated. A comparative study between skin test and specific IgE responses to the antigens studied was carried out in 428 consecutive allergic subjects.

RESULTS

All the tests performed suggested that cross-reacting carbohydrate epitopes were the cause of false-positive specific IgE results in one of the commercial systems and the high reactivity in all the solid-phase in vitro tests. None of the cross-reacting carbohydrate allergens yielded a positive skin test response. Periodate treatment caused variable degrees of reduction of IgE binding to the different antigens studied, indicating that CCDs played a different role in each of them. About 41% of patients allergic to pollen had specific IgE for a glycoprotein, without a positive skin test response to the same molecule.

CONCLUSIONS

CCDs must be taken into account when evaluating the clinical relevance of positive results in in vitro specific IgE assays, at least in the diagnosis of patients with pollen allergy. Commercial systems should be carefully assessed for the ability to detect specific IgE for carbohydrate determinants to avoid false-positive or clinically irrelevant results.

Detection of allergen-induced basophil activation by expression of CD63 antigen using a tricolour flow cytometric method

In the field of allergy diagnosis, most in vitro functional tests are focused on basophils. Nevertheless, the very small number of circulating basophils limits these experiments and their clinical benefit remains controversial. As flow cytometry is a valuable tool for identifying cell populations, even at low concentrations, we developed a tricolour flow cytometric method for the study of allergen-induced basophil activation. Identification of cells was based both on CD45 expression and on the presence of IgE on the cell surface, since basophils express high-affinity receptors for IgE (Fc epsilon RI). Cell activation upon allergen challenge was assessed by the expression of CD63 antigen on the plasma membrane. Basophil isolation and activation (with the chemotactic peptide formyl-methionyl-leucyl-phenylalanine) were validated in 32 non-allergic patients. In 12 allergic patients, basophil stimulation by a relevant allergen was in most cases positive (10/12). Furthermore a concentration-dependent hook effect was observed. Of the allergic and non-allergic patients, none showed non-specific activation with an irrelevant allergen (specificity 100%). Overall, our preliminary results, even in a small population, suggest that this is a reliable and valuable method for the diagnosis of allergies complementing specific allergen IgE and skin test results. Obviously, additional clinical studies are needed to validate these first results.