Neutrophil-intrinsic TNF receptor signaling orchestrates host defense against Staphylococcus aureus

Staphylococcus aureus is the leading cause of skin and soft tissue infections and is a major health burden due to the emergence of antibiotic-resistant strains. To address the unmet need of alternative treatments to antibiotics, a better understanding of the protective immune mechanisms against S. aureus skin infection is warranted. Here, we report that tumor necrosis factor (TNF) promoted protection against S. aureus in the skin, which was mediated by bone marrow-derived immune cells. Furthermore, neutrophil-intrinsic TNF receptor (TNFR) signaling directed immunity against S. aureus skin infections. Mechanistically, TNFR1 promoted neutrophil recruitment to the skin, whereas TNFR2 prevented systemic bacterial dissemination and directed neutrophil antimicrobial functions. Treatment with a TNFR2 agonist showed therapeutic efficacy against S. aureus and Pseudomonas aeruginosa skin infections, which involved increased neutrophil extracellular trap formation. Our findings revealed nonredundant roles for TNFR1 and TNFR2 in neutrophils for immunity against S. aureus and can be therapeutically targeted for protection against bacterial skin infections.

Crisaborole efficacy in murine models of skin inflammation and Staphylococcus aureus infection

Phosphodiesterase 4 (PDE4) is highly expressed in keratinocytes and immune cells and promotes pro-inflammatory responses upon activation. The activity of PDE4 has been attributed to various inflammatory conditions, leading to the development and approval of PDE4 inhibitors as host-directed therapeutics in humans. For example, the topical PDE4 inhibitor, crisaborole, is approved for the treatment of mild-to-moderate atopic dermatitis and has shown efficacy in patients with psoriasis. However, the role of crisaborole in regulating the immunopathogenesis of inflammatory skin diseases and infection is not entirely known. Therefore, we evaluated the effects of crisaborole in multiple mouse models, including psoriasis-like dermatitis, AD-like skin inflammation with and without filaggrin mutations, and Staphylococcus aureus skin infection. We discovered that crisaborole dampens myeloid cells and itch in the skin during psoriasis-like dermatitis. Furthermore, crisaborole was effective in reducing skin inflammation in the context of filaggrin deficiency. Importantly, crisaborole reduced S. aureus skin colonization during AD-like skin inflammation. However, crisaborole was not efficacious in treating S. aureus skin infections, even as adjunctive therapy to antibiotics. Taken together, we found that crisaborole reduced itch during psoriasis-like dermatitis and decreased S. aureus skin colonization upon AD-like skin inflammation, which act as additional mechanisms by which crisaborole dampens the immunopathogenesis in mouse models of inflammatory skin diseases. Further examination is warranted to translate these preclinical findings to human disease.

CCR2 contributes to host defense against Staphylococcus aureus orthopedic implant-associated infections in mice

C-C motif chemokine receptor 2 (CCR2) is an important mediator of myeloid cell chemotaxis during inflammation and infection. Myeloid cells such as monocytes, macrophages, and neutrophils contribute to host defense during orthopedic implant-associated infections (OIAI), but whether CCR2-mediated chemotaxis is involved remains unclear. Therefore, a Staphylococcus aureus OIAI model was performed by surgically placing an orthopedic-grade titanium implant and inoculating a bioluminescent S. aureus strain in knee joints of wildtype (wt) and CCR2-deficient mice. In vivo bioluminescent signals significantly increased in CCR2-deficient mice compared with wt mice at later time points (Days 14-28), which was confirmed with ex vivo colony-forming unit enumeration. S. aureus γ-hemolysin utilizes CCR2 to induce host cell lysis. However, there were no differences in bacterial burden when the OIAI model was performed with a parental versus a mutant γ-hemolysin-deficient S. aureus strain, indicating that the protection was mediated by the host cell function of CCR2 rather than γ-hemolysin virulence. Although CCR2-deficient and wt mice had similar cellular infiltrates in the infected joint tissue, CCR2-deficient mice had reduced myeloid cells and γδ T cells in the draining lymph nodes. Taken together, CCR2 contributed to host defense at later time points during an OIAI by increasing immune cell infiltrates in the draining lymph nodes, which likely contained the infection and prevented invasive spread.

Pan-caspase inhibition as a potential host-directed immunotherapy against MRSA and other bacterial skin infections

Staphylococcus aureus causes most skin infections in humans, and the emergence of methicillin-resistant S. aureus (MRSA) strains is a serious public health threat. There is an urgent clinical need for nonantibiotic immunotherapies to treat MRSA infections and prevent the spread of antibiotic resistance. Here, we investigated the pan-caspase inhibitor quinoline-valine-aspartic acid-difluorophenoxymethyl ketone (Q-VD-OPH) for efficacy against MRSA skin infection in mice. A single systemic dose of Q-VD-OPH decreased skin lesion sizes and reduced bacterial burden compared with vehicle-treated or untreated mice. Although Q-VD-OPH inhibited inflammasome-dependent apoptosis-associated speck-like protein containing caspase activation and recruitment domain (ASC) speck formation and caspase-1-mediated interleukin-1β (IL-1β) production, Q-VD-OPH maintained efficacy in mice deficient in IL-1β, ASC, caspase-1, caspase-11, or gasdermin D. Thus, Q-VD-OPH efficacy was independent of inflammasome-mediated pyroptosis. Rather, Q-VD-OPH reduced apoptosis of monocytes and neutrophils. Moreover, Q-VD-OPH enhanced necroptosis of macrophages with concomitant increases in serum TNF and TNF-producing neutrophils, monocytes/macrophages, and neutrophils in the infected skin. Consistent with this, Q-VD-OPH lacked efficacy in mice deficient in TNF (with associated reduced neutrophil influx and necroptosis), in mice deficient in TNF/IL-1R and anti-TNF antibody-treated WT mice. In vitro studies revealed that combined caspase-3, caspase-8, and caspase-9 inhibition reduced apoptosis, and combined caspase-1, caspase-8, and caspase-11 inhibition increased TNF, suggesting a mechanism for Q-VD-OPH efficacy in vivo. Last, Q-VD-OPH also had a therapeutic effect against Streptococcus pyogenes and Pseudomonas aeruginosa skin infections in mice. Collectively, pan-caspase inhibition represents a potential host-directed immunotherapy against MRSA and other bacterial skin infections.

Interleukin-1β and tumor necrosis factor are essential in controlling an experimental orthopedic implant-associated infection

Orthopedic implant-associated infection (OIAI) is a major complication that leads to implant failure. In preclinical models of Staphylococcus aureus OIAI, osteomyelitis and septic arthritis, interleukin-1α (IL-1α), IL-1β, and tumor necrosis factor (TNF) are induced, but whether they have interactive or distinctive roles in host defense are unclear. Herein, a S. aureus OIAI model was performed in mice deficient in IL-1α, IL-1β, or TNF. Mice deficient in IL-1β or TNF (to a lesser extent) but not IL-1α had increased bacterial burden at the site of the OIAI throughout the 28-day experiment. IL-1β and TNF had a combined and critical role in host defense as mice deficient in both IL-1R and TNF (IL-1R/TNF-deficient mice) had a 40% mortality rate, which was associated with markedly increased bacterial burden at the site of the OIAI infection. Finally, IL-1α- and IL-1β-deficient mice had impaired neutrophil recruitment whereas IL-1β-, TNF-, and IL-1R/TNF-deficient mice all had impaired recruitment of both neutrophils and monocytes. Therefore, IL-1β and TNF contributed to host defense against S. aureus OIAI and neutrophil recruitment was primarily mediated by IL-1β and monocyte recruitment was mediated by both IL-1β and TNF.

Rabbit model of Staphylococcus aureus implant-associated spinal infection

Post-surgical implant-associated spinal infection is a devastating complication commonly caused by Staphylococcus aureus. Biofilm formation is thought to reduce penetration of antibiotics and immune cells, contributing to chronic and difficult-to-treat infections. A rabbit model of a posterior-approach spinal surgery was created, in which bilateral titanium pedicle screws were interconnected by a plate at the level of lumbar vertebra L6 and inoculated with a methicillin-resistant S.aureus (MRSA) bioluminescent strain. In vivo whole-animal bioluminescence imaging (BLI) and ex vivo bacterial cultures demonstrated a peak in bacterial burden by day 14, when wound dehiscence occurred. Structures suggestive of biofilm, visualized by scanning electron microscopy, were evident up to 56 days following infection. Infection-induced inflammation and bone remodeling were also monitored using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and computed tomography (CT). PET imaging signals were noted in the soft tissue and bone surrounding the implanted materials. CT imaging demonstrated marked bone remodeling and a decrease in dense bone at the infection sites. This rabbit model of implant-associated spinal infection provides a valuable preclinical in vivo approach to investigate the pathogenesis of implant-associated spinal infections and to evaluate novel therapeutics.

Summary: A model of post-surgical methicillin-resistant Staphylococcus aureus implant-associated spinal infection was created in rabbits, recapitulating acute infection as well as chronic low-burden infection, with structures suggestive of biofilm formation and bone remodeling.

Development of a Staphylococcus aureus reporter strain with click beetle red luciferase for enhanced in vivo imaging of experimental bacteremia and mixed infections

In vivo bioluminescence imaging has been used to monitor Staphylococcus aureus infections in preclinical models by employing bacterial reporter strains possessing a modified lux operon from Photorhabdus luminescens. However, the relatively short emission wavelength of lux (peak 490 nm) has limited tissue penetration. To overcome this limitation, the gene for the click beetle (Pyrophorus plagiophtalamus) red luciferase (luc) (with a longer >600 emission wavelength), was introduced singly and in combination with the lux operon into a methicillin-resistant S. aureus strain. After administration of the substrate D-luciferin, the luc bioluminescent signal was substantially greater than the lux signal in vitro. The luc signal had enhanced tissue penetration and improved anatomical co-registration with infected internal organs compared with the lux signal in a mouse model of S. aureus bacteremia with a sensitivity of approximately 3 × 10⁴ CFU from the kidneys. Finally, in an in vivo mixed bacterial wound infection mouse model, S. aureus luc signals could be spectrally unmixed from Pseudomonas aeruginosa lux signals to noninvasively monitor the bacterial burden of both strains. Therefore, the S. aureus luc reporter may provide a technological advance for monitoring invasive organ dissemination during S. aureus bacteremia and for studying bacterial dynamics during mixed infections.

Scope and Safety of Paediatric Surgery in a Model III Hospital

Introduction Elective and emergency paediatric general surgery is performed in numerous hospitals but with differing exclusion and transfer thresholds. Recent national guidelines detail necessary surgical, anaesthetic and nursing resources for safe and efficient delivery of services. Methods A retrospective review of paediatric surgical admissions was performed from January 2015 to December 2016. Charts of prolonged admissions or readmissions were reviewed. Results There was a total of 2,079 surgical admissions. 575 (27.2%) were elective and 1504 (71.2%) were emergency admissions. Significantly more surgical procedures were performed in 2016 (n=546, 56% versus n=433, 44.2%). Laparoscopic appendicectomy was the most commonly performed procedure. Re-admission rates were lower in 2016 (n=9, 0.8% versus n=21, 2.2%). All complications were Clavien-Dindo Grade I or II. Discussion Paediatric general surgery can be safely and efficiently performed by staffed and resourced Model III hospitals.

Prospective comparison of outcome after treatment for triple-negative and non-triple-negative breast cancer

INTRODUCTION

Triple-negative breast cancers (TNBC) are associated with a poor prognosis owing to an aggressive phenotype. We aimed to carry out a prospective study comparing management strategies and response to therapy in TNBC and non-TNBC patients.

METHODS

Data were obtained from a prospectively maintained database of patients treated for breast cancer.

RESULTS

A total of 142 TNBC and 142 age-, stage- and NPI-matched non-TNBC patients were treated. The difference in overall survival between the 2 groups was statistically significant (77% of TNBC patients alive at a mean follow-up of 32 months, versus 92% of non-TNBC patients at a mean follow-up of 38 months, P = 0.0 Log rank test). This survival difference was found to be independent of NPI (P = 0.0 Log rank test). Locoregional recurrence rates were similar between TNBC patients who were treated with wide local excision versus mastectomy (P = 0.449 Log rank test). A significant difference in survival was noted between TNBC patients who responded differentially to neoadjuvant chemotherapy (P = 0.035 Log rank test).

CONCLUSION

Patients with TNBC have adverse outcomes despite aggressive treatment. The development of effective targeted therapies is essential for this breast cancer subtype.

Breast clinic referrals: can mastalgia be managed in primary care?

BACKGROUND

Centralisation of breast cancer services in Ireland has resulted in a significant increase in the number of patients attending symptomatic breast units (SBU). A considerable proportion of patients referred to SBU present with non-suspicious symptoms and fall into a "low-risk" category for breast cancer. It has been proposed that consideration be given to a primary care-delivered service for these patients.

AIM

To evaluate SBU attendances and correlate with diagnosis to identify a cohort of patients who may be suitable for management in the primary care setting.

METHODS

Data were collected from a prospectively maintained database on patients attending SBU at two tertiary referral centres (Beaumont Hospital and University College Hospital Galway) from January 2011 to 2012. Reasons for attendance, outcome of triple-assessment and incidence of malignancy were analysed.

RESULTS

14,325 patients underwent triple assessment at the SBU in this time period. 5,841 patients were referred with mastalgia, of whom 3,331 (57 %) reported mastalgia as the only symptom. The incidence of breast cancer in patients presenting with mastalgia alone was 1.2 %. All patients diagnosed with breast cancer in this cohort were over 35 years of age.

CONCLUSION

The incidence of breast cancer in patients referred to SBU with mastalgia as an isolated symptom is extremely low. Patients under 35 years of age, with mastalgia as an isolated symptom do not require breast imaging and have a sufficiently low risk of breast cancer that they may be suitable for management in the primary care setting.

Percutaneous transhepatic cholecystoscopic gallstone fragmentation: a novel approach for the medically unfit patient?

Management of the surgically unfit patient with symptomatic cholelithiasis can be fraught with difficulty. We describe the case of on such gentleman in whom percutaneous transhepatic cholecystoscopy was used to completely fragment a large gallbladder calculus through the use of a nephroscope and Swiss lithoclast Master.

Is there a requirement for axillary lymph node dissection following identification of micro-metastasis or isolated tumour cells at sentinel node biopsy for breast cancer?

INTRODUCTION

Recent decades have seen a significant shift towards conservative management of the axilla. Increasingly, immunohistochemical analysis of sentinel nodes leads to the detection of small tumour deposits, the significance of which remains uncertain. The aims of this study are to examine patients whose sentinel lymph nodes are positive for macro-metastasis, micro-metastasis or isolated tumour cells (ITCs) and to determine the rate of further nodal disease after axillary lymph node dissection (ALND).

METHODS

A retrospective analysis of all patients undergoing a sentinel lymph node biopsy (SLNB) between January 2007 and December 2010 in a tertiary referral breast unit was performed. Patients who underwent an axillary lymph node dissection for macro-metastasis, micro-metastasis or ITCs were identified. Demographics, histological data and the rate of further axillary disease were examined.

RESULTS

In total, 664 breast cancer patients attended the symptomatic breast unit during the study period, 360 of whom underwent a SLNB. Seventy patients had a SLNB positive for macro-metastasis. All of these patients underwent ALND. A positive SLNB with either micro-metastasis or ITCs was identified in 58 patients. Only 41 of the 58 patients went on to have an ALND, due primarily to variations in surgeons' preferences. Nineteen patients with micro-metastasis underwent an ALND. Four patients had further axillary disease (21%). Twenty-two patients had ITCs identified, of whom only one had further disease (4.5%). No statistically significant difference was found between the two groups in terms of tumour size, grade, lymphovascular invasion or oestrogen receptor status.

CONCLUSION

ALND should be considered in patients with micro-metastasis at SLNB. It should rarely be employed in the setting of SLNB positive for ITCs.

Psychological functioning and quality of life in lung transplant candidates and recipients

OBJECTIVE

The purpose of this study was to examine the psychological functioning and quality of life (QOL) of lung transplant candidates and recipients.

METHODS

The following measures were completed by 36 lung transplant candidates (the pretransplant group [PRE]) and 73 recipients (the posttransplant group [POST]): the Rand-36 Item Health Survey 1.0 (RAND-36), visual analog scale of overall QOL (OQOL), Brief Symptoms Inventory (BSI), Derogatis Sexual Functioning Inventory (DSFI), Hospital Anxiety and Depression Scale (HAD), Rosenberg Self-Esteem Scale (RSES), and Body Cathexis Scale (BC).

RESULTS

Compared to the PRE, POST patients had significantly better scores on the following measures: RAND-36 total, physical health, role limitations due to physical health, general health, vitality, and social functioning subscales (all p < 0.0001); visual analog scale of OQOL (p < 0.0001); BSI (p < 0.05); BC (p < 0.05); HAD anxiety (p < 0.05) and depression (p < 0.0001); and RSES (p < 0.05). Despite better scores, some areas did not differ between the PRE and the POST, and many patients continued to experience impairments in psychological functioning. Specifically, the RAND-36 emotional health and role limitations due to emotional health subscale scores did not differ between the PRE and the POST and they remained lower than published norms. A significant proportion of patients in both groups (44% of PRE patients and 28% of POST patients) had borderline or clinical levels of anxiety (ie, the HAD). Finally, PRE and POST mean scores were significantly lower than published norms on the RSES (p < 0.05) and the body image scale of the DSFI (p < 0.05).

CONCLUSIONS

Although lung transplant recipients have better general, physical, and psychological health than their pretransplant counterparts, the present research suggests that both groups experience impairment in several areas of psychological functioning. Future research into the QOL of the lung transplant population should be aimed at recognizing, intervening, and improving patients' psychological and emotional well-being.

The placebo effect in asthma drug therapy trials: a meta-analysis

A meta-analysis of randomized controlled asthma drug therapy trials published in the English literature from January 1991 to June 1995 was performed to estimate the magnitude and direction of the placebo effect in stable ambulatory asthmatic patients. Among placebo groups, the mean absolute increase in forced expiratory volume in 1 sec (FEV1), weighted for sample size and variance, was 0.11 L/min, and the mean percent increase in FEV1 was 4.81%. The corresponding placebo group changes in peak expiratory flow (PEF) were in an opposite direction to those of FEV1; there was a mean absolute decrease of 2.24 L/min, and a mean percent decrease of 4.21%. Changes for active treatment groups were greater in magnitude. However, there were no statistically significant differences in mean changes comparing the placebo groups to the treatment groups, for any of the outcome measures. Mean increases in PEF and FEV1 exceeded 10% in 5 of 33 placebo groups, as compared to 13 of 33 active treatment groups. In conclusion, in well-designed long-term drug therapy studies in stable asthmatics the pooled placebo effect is small but measurable, with FEV1 and PEF showing different directions of response. Moreover, a modest number of patients receiving placebo have changes in pulmonary function that might be interpreted as clinically significant.

Use of inhaled medications and urgent care services. Study of Canadian asthma patients

OBJECTIVE

To determine asthma patients' patterns of disease and knowledge of asthma.

DESIGN

Telephone survey of patients with diagnosed asthma.

SETTING

Residences in 10 Canadian provinces.

PARTICIPANTS

Patients with asthma diagnosed by a doctor: 829 men and women with a mean age of 38 +/- 7 years.

MAIN OUTCOME MEASURES

Classes of asthma medications, patterns of use, frequency and severity of asthma symptoms use of emergency departments and urgent medical services, participation in asthma education programs, presence of environmental triggers, and knowledge of asthma pathophysiology and treatment.

RESULTS

Four hundred fifty-six patients (55%) reported daily symptoms of asthma; 431 patients (52%) used inhaled beta 2-agonists daily. Only 340 patients (41%) used inhaled corticosteroids (IC), and many used them irregularly. A total of 579 (72%) respondents reported no unscheduled visits to a family physician for worsening asthma, but one third of patients had been to an emergency department for uncontrolled asthma in the last 5 years, and most of these visits had occurred during the last year. As to knowledge, 406 patients (49%) disagreed with the statement that asthma is a lifelong condition that cannot be cured. Among IC users, only 101 (30%) knew that IC reduced airway inflammation; among beta 2-agonist users, only 33% agreed that beta 2-agonists opened the bronchial tubes. Two hundred forty patients (29%) reported being current cigarette smokers, and 381 (46%) reported having pets at home.

CONCLUSIONS

Daily symptoms and daily use of beta 2-agonists are common among Canadian asthma patients, and this is in excess of what is considered acceptable by current asthma care guidelines. Underuse of IC, inadequate knowledge of asthma symptoms and treatments, and failure to avoid asthma triggers were common in the population studied.

Asthma and allergy avoidance knowledge and behavior in postpartum women

OBJECTIVE

Based on family history, infants may be classified as "high risk" or "low risk" for the development of allergy or asthma. Failure to breast-feed and early exposure to cigarette smoke or aeroallergens increase the risk of developing asthma or allergy. Since we suspect that physicians seldom educate mothers on reducing environmental exposures in the postnatal period, we sought to determine the level of maternal knowledge as well as actual avoidance behaviors with respect to these risk factors in high risk and low risk families.

DESIGN

Questionnaire administered by a research assistant.

SETTING

Obstetrics unit of two tertiary care general hospitals.

PATIENTS

A sample of 194 postpartum women with uncomplicated pregnancies, interviewed after 24-hours postpartum.

MAIN OUTCOME MEASURES

(1) Parental history of asthma, allergy or eczema; (2) potential for infant exposure to environmental risk factors for asthma and allergy, as indicated by history of avoidance practices in the home; (3) parental knowledge of risk factors for asthma or allergy; and (4) physician advise on avoidance.

RESULTS

Of 194 women interviewed, a history of doctor-diagnosed asthma, allergy/allergic rhinitis or eczema in either parent was reported by 122 (high risk group). The remaining 72 patients had no history of atopy (low risk group). Of those in the high risk group, 10% of mothers smoked during pregnancy, and about 25% were exposed to second hand smoke on a daily basis. Most of the mothers in the high risk group planned to breast feed (89%). A large number of patients in the high risk group reported potential risk factors for allergy/asthma in their home environments. These included animals in the household (36%), dusty environments (10%) carpeting (47%), cigarette smoke (18%), and others. Despite these risks, only 13% of patients reported being educated by their physicians on improving their home environment. Exposures to environmental risk factors were not different between low and high risk groups. Similarly, knowledge of environmental risk factors and avoidance behaviors were not significantly different between low and high risk groups.

CONCLUSIONS

Many mothers whose infants are at high risk of developing asthma or allergies are not aware of and do not practice avoidance of risk factors. Physicians involved in prenatal care of women with a family history of atopy and asthma should offer advice on reducing exposure to potential risk factors and how to modify their environment in ways that can potentially decrease the risk of asthma or allergy prevalence and severity.

Prehospitalization inhaled corticosteroid use in patients with COPD or asthma

BACKGROUND

Guidelines for the treatment of obstructive lung diseases suggest a primary role of inhaled corticosteroids (ICs) in asthma, but only a minor role in COPD. However, surveys of physicians' prescribing habits have suggested that there is little difference in the use of ICs between these two conditions.

OBJECTIVES

To determine the prevalence of IC use before and during hospitalization among patients with COPD or asthma.

DESIGN

Retrospective chart review.

SETTING

Tertiary care university teaching hospital.

PATIENTS

Adult inpatients, aged 18 or older, with physician-diagnosed COPD or asthma.

MEASUREMENTS

Patient-reported prescription drug use at hospital admission, and medical chart record of in-hospital and discharge prescriptions.

RESULTS

Of 350 charts reviewed, 102 patients were admitted to the hospital for unstable COPD, 133 patients had stable COPD, 36 patients were admitted with unstable asthma, and 79 patients had stable asthma. At hospital admission, 48% of unstable COPD patients, 26% of stable COPD patients, 56% of unstable asthma patients, and 44% of stable asthma patients reported having a current prescription for ICs. The proportion of all asthmatic patients reporting a current prescription for ICs at admission (48%) was significantly higher than the proportion of all COPD patients receiving an IC at admission (35%). However, there was no significant difference in the proportion of COPD and asthma patients with a current prescription of any form of corticosteroid (oral or inhaled). The proportion of COPD patients likely to respond to IC therapy is significantly different from the observed use at hospital admission.

CONCLUSIONS

The proportion of patients found to be using ICs is much higher than the proportion expected to respond. There was little difference in the use of ICs for asthma and COPD patients at hospital admission. Most COPD patients using an IC were receiving the regimen on admission to hospital, indicating that there is need for education in the community and in the hospital regarding use of ICs in COPD patients.

Prior diagnosis and treatment of patients with normal results of methacholine challenge and unexplained respiratory symptoms

OBJECTIVE

Previous research indicates that asthma has been underdiagnosed. However, we suspect that recent widespread attention to the underdiagnosis of asthma has led to an overdiagnosis of asthma in some settings. We therefore sought to examine prior diagnosis and treatment of patients referred to our facility and subsequently found to have no objective evidence of variable airflow limitation.

DESIGN

Retrospective chart review.

SETTING

Hospital-based asthma center.

PATIENTS

A referred sample of 263 patients in whom a methacholine challenge (MCC) was conducted after evaluation by our pulmonologists; complete medical histories were available.

MAIN OUTCOME MEASURES

Prior respiratory diagnoses, duration of treatment with asthma medications, and diagnosis following assessment by our pulmonologists in 175 patients with a provocative concentration of the substance causing a 20% fall in FEV1 (PC20) greater than 8.0 mg/mL and 88 with a PC20 of 8.0 mg/mL or less.

RESULTS

Of those with a PC20 greater than 8 mg/mL, a diagnosis of asthma or possible asthma prior to the challenge study was recorded by their primary care physician in 129 patients (74%). One hundred sixty of 172 patients (88%) with a PC20 greater than 8 mg/mL were diagnosed as not having asthma by our pulmonologists; 109 of 172 patients (62%) had been previously treated with asthma medication(s). The mean duration of asthma treatment was 25.9+/- 56.3 months, and there was no significant difference in the duration of treatment between this group and those who had a PC20 of 8 mg/mL or less. Most of those treated received inhaled beta2-agonists and inhaled corticosteroids. Approximately 61% received two or more classes of medications.

CONCLUSIONS

The misdiagnosis of asthma occurs commonly in the referral practice of a tertiary care asthma center. The more frequent use of objective pulmonary function testing in primary practice might reduce the problem of delayed diagnosis and inappropriate therapy for respiratory symptoms.