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Divisions of a Rheumatology
b Immunology/Allergy, Department of Pediatrics
c Division of Transfusion Medicine, Department of Pediatric Laboratory Medicine
d Department of Health Policy Management and Evaluation
e Department of Public Health Sciences, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada
| ABSTRACT |
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PATIENTS AND METHODS. The intravenous immunoglobulin infusion history (product given and history of adverse events) of patients who were attending the juvenile dermatomyositis clinic at the Hospital for Sick Children from 1986 to 2005 was reviewed. Products with an immunoglobulin A content of >15 µg/mL were classified as "high immunoglobulin A." Data were analyzed by using logistic regression models adjusted for repeated measures.
RESULTS. Thirty-eight patients with juvenile dermatomyositis received 1056 infusions at the Hospital for Sick Children. Adverse events were reported on 92 occasions (9%), affecting 25 patients (66%), a frequency that is higher than that usually reported in adult patients (<1%–5%). Adverse events were reported more often with products that contained high immunoglobulin A (15.0% vs 8.0%). These were accounted for specifically by fever (8.0% vs 1.0%), lethargy or malaise (2.0% vs 0.1%), and nausea or vomiting (5.0% vs 1.0%). Of the possible pharmacologic predictors, including dose, immunoglobulin G concentration, immunoglobulin A level, pH, glycine content, sugar content, sodium content, and osmolality, only immunoglobulin A level was significantly associated with adverse events.
CONCLUSIONS.Intravenous immunoglobulin was found to be safe and well tolerated by most children with juvenile dermatomyositis. However, in contrast to adult studies, we found that significant differences existed in tolerance to different intravenous immunoglobulin products, most likely because of immunoglobulin A concentration. This study confirms anecdotal reports that a high level of immunoglobulin A in intravenous immunoglobulin is less well tolerated by children and provides evidence that product choice is important in pediatrics.
Key Words: immunoglobulin (intravenous) IgA drug safety dermatomyositis (juvenile)
Abbreviations: IVIg—intravenous immunoglobulin JDM—juvenile dermatomyositis IgA—immunoglobulin A
Human intravenous immunoglobulin (IVIg) transfusion was introduced in the early 1950s as a therapeutic agent for the treatment of primary and secondary immunodeficiency.1 In the past 2 decades its use has been extended; IVIg is now often used as an adjunctive therapy for juvenile dermatomyositis (JDM) and other neuromuscular disorders.2 Efficacy in the treatment of adult dermatomyositis3,4 and other adult neuromuscular disorders5,6 has already been established, and initial studies strongly suggest that IVIg is also efficacious for pediatric patients.7 IVIg is now widely used for many diseases in both adult and pediatric populations.
Although the human IgG molecule is the active agent in all IVIg products, differences in production processes have resulted in preparations with diverse pharmacologic composition.8 Questions have been raised about possible differences in efficacy and safety between the different commercial IVIgs.9 To date, most prospective trials in adult populations have found no differences in efficacy and safety between different IVIg products.10,11 These results contradict recurrent anecdotal reports of differences in the frequency of adverse events between IVIg preparations when administered to pediatric patients. However, perhaps because of the relatively low number of children receiving IVIg at any given time, the significant heterogeneity in the type of patients receiving IVIg, and the inconsistencies in product availability, long-term prospective trials evaluating IVIg tolerance in children have not been done, and these suspicions have not been formally tested.
Although IVIg infusion is considered to be a very safe treatment, adverse events, such as headaches, nausea, fever, abdominal cramps, malaise, lethargy, myalgia, and arthralgia, are commonly observed. Life-threatening reactions to IVIg are very rare but have sporadically been reported.12 Differences in preparation, mainly product concentration, sodium content, pH, and osmolality, have been hypothesized as potential risk factors for product intolerance.13 Differences in immunoglobulin A (IgA) content have not usually been considered important risk factors (except when administered to patients with IgA deficiency).
Considering our experience, IgA content may have been overlooked as a potential risk factor for IVIg tolerability. In this study we asked whether, for children with JDM, the different IVIg preparations are equally tolerated, and, if not, whether those that contain high IgA are associated with an increased frequency of adverse events.
| METHODS |
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IVIg therapy for JDM is often given over a long course of
2.5 years, although wide variations in treatment duration can be observed. The infusion protocol used was standardized for this population.
After research ethics board approval was obtained, blood transfusion records were obtained from the hospital pharmacy (1986–1995) and blood transfusion laboratory (1996–2005) and were cross-validated with the patient medical chart. Nursing notes for every IVIg transfusion were reviewed by an independent assessor blinded to product assignment. Adverse events were defined and classified according to the hospital "Blood Transfusion Reaction Report" (form No. 35639, December 2005 revision). Patients who developed adverse events to IVIg were often premedicated for subsequent infusions (with antihistamines and/or corticosteroids).
Patients received 1 of 4 IVIg products during the study period: Iveegam EN 5% (Baxter International Inc, Deerfield, IL), Gammagard S/D 5% (Baxter International Inc, Deerfield, IL, introduced in 1994), Gamimune N 5% (Bayer Healthcare, Research Triangle Park, NC, discontinued in 1994) and Gamimune N 10% (Bayer Healthcare, Research Triangle Park, NC, introduced in 1999). Product assignment depended on availability; however, Iveegam, when available, was preferentially used because of the suspected lower frequency of adverse reactions (based on the treating physicians' previous experience). Each product's ingredients were obtained from the product monograph (Table 1). Iveegam (10 µg of IgA per mL) and Gammagard (2.2 µg of IgA per mL) were classified as having low IgA levels, whereas Gamimune N 5% (270 µg of IgA per mL) and Gamimune N 10% (270 µg of IgA per mL) were classified as having high IgA levels.
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| RESULTS |
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The frequency of adverse events was not similar between IVIg preparations (Table 3). Gammagard was associated with the lowest frequency of adverse events, followed by Iveegam, and finally by Gamimune. The reactions most commonly reported were fever, headaches, nausea or vomiting, and lethargy. Arthralgia, myalgia, hives, urticaria, chills, dizziness, hypertension, back pain, chest pain, and abdominal pain were uncommonly reported.
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| DISCUSSION |
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The frequency of adverse reactions that we observed is higher than that usually reported in adult populations (<1%–5%),15 which suggests that children may be less tolerant to IVIg than adults; however, differences in adverse event reporting cannot be ruled out. In addition, because we only studied children with JDM, it may be that some of the adverse reactions that we observed are specific for this condition (eg, it may be that patients with autoimmune diseases such as JDM, who have a hyperactive immune system, react more to exogenous IgA). Given that we observed a lower frequency of adverse events after the initial infusion, premedication of patients with initial intolerance to IVIg should be seriously considered.
In contrast to previous studies, age at infusion was not found to affect the frequency of adverse events.16 In addition, although our finding that adverse reactions are more likely on the first infusion has been reported previously, we believe that, in our cohort, it is more likely because of the premedicating of patients after the first infusion rather than reflecting habituation, as suggested previously.16 Osmolality, sodium content, and preparation concentration were not found to affect tolerance. These results differ from earlier work.17
Differences in IVIg product tolerance because of IgA content could be explained by an Fc-
receptor present on white blood cells that is activated through direct interaction with IgA. The interaction of the Fc-
receptor with IgA is a potent trigger of metabolic activation of mast cells, leading to degranulation and to superoxide release from granulocytes and monocytes.18 Mast cell degranulation leads to the release of histamine, tumor necrosis factor-
, and heparin, all of which are potent inducers of fever.19 Therefore, biological activation of IgA receptors may result in an increase of postinfusion fevers in high-IgA IVIg preparations. Children may have a higher sensitivity to immunologic triggers than adults; in the case of IVIg reactions, introduction of a relatively high dose of foreign IgA might explain why children seem to be less tolerant to IVIg than adults.
It might be argued that potential differences in IVIg product efficacy might be a more compelling reason to choose specific IVIg products rather than adverse reactions, especially when considering that adverse events were uncommon and that no life-threatening events were observed in this cohort. However, because few studies to date have found differences in IVIg product efficacy, we believe that tolerability is a reasonable guide to preparation choice.
Our results must be considered in the light of the possible limitations resulting from our study design. Our study was retrospective, and it is possible that, because of incomplete medical charts, adverse events might not have been recorded, leading to a potential underestimation of adverse events. However, the infusion protocol and patient monitoring was followed strictly, and adverse events reports were not in any way dependent on product assignment. Therefore, we believe that any underestimation introduced in our assessment would be equally distributed across products and would not affect the relationship between different products or the relationship between IgA concentration and adverse reactions.
Because most studies have not found differences in product efficacy in pediatrics, product tolerability should be the primary guideline in selecting an IVIg preparation; IVIg is often a long-term treatment, and adverse reactions to infusions can hamper patients' quality of life. Our study suggests that, when the option is available, IVIg products with low IgA content should be selected for the treatment of children with JDM and should be considered for children with other indications.
| ACKNOWLEDGMENTS |
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We acknowledge the work of Christina Goia and Derek Stephens from the Child Health Evaluative Services at the Hospital for Sick Children for advice and review of the statistical analysis, and we acknowledge Dr Brian R. Beven (Department of Pharmacy) for providing IVIg infusion records.
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Address correspondence to Brian M. Feldman, MD, MSc, FRCP(C), 555 University Ave, Toronto, Ontario, Canada M5G 1X8. E-mail: brian.feldman{at}sickkids.ca
Financial Disclosure: Dr Feldman holds research grants funded by Bayer Inc; the other authors have indicated they have no financial relationships relevant to this article to disclose.
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