129Xe MRI Ventilation Textures and Longitudinal Quality-of-Life Improvements in Long-COVID

RATIONALE AND OBJECTIVES

It remains difficult to predict longitudinal outcomes in long-COVID, even with chest CT and functional MRI. 129Xe MRI reflects airway dysfunction, measured using ventilation defect percent (VDP) and in long-COVID patients, MRI VDP was abnormal, suggestive of airways disease. While MRI VDP and quality-of-life improved 15-month post-COVID infection, both remained abnormal. To better understand the relationship of airways disease and quality-of-life improvements in patients with long-COVID, we extracted 129Xe ventilation MRI textures and generated machine-learning models in an effort to predict improved quality-of-life, 15-month post-infection.

MATERIALS AND METHODS

Long-COVID patients provided written-informed consent to 3-month and 15-month post-infection visits. Pyradiomics was used to extract 129Xe ventilation MRI texture features, which were ranked using a Random-Forest classifier. Top-ranking features were used in classification models to dichotomize patients based on St. George's Respiratory Questionnaire (SGRQ) score improvement greater than the minimal-clinically-important-difference (MCID). Classification performance was evaluated using the area under the receiver-operator-characteristic-curve (AUC), sensitivity, and specificity.

RESULTS

120 texture features were extracted from 129Xe ventilation MRI in 44 long-COVID participants (54 ± 14 years), including 30 (52 ± 12 years) with ΔSGRQ≥MCID and 14 (58 ± 18 years) with ΔSGRQ

CONCLUSION

A machine learning model exclusively trained on 129Xe MRI ventilation textures explained improved SGRQ-scores 12 months later, and outperformed clinical models. Their unique spatial-intensity information helps build our understanding about long-COVID airway dysfunction.

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Affiliation(s)

Harkiran K Kooner Robarts Research Institute, Western University, London, Canada; Department of Medical Biophysics, Western University, London, Canada
Maksym Sharma Robarts Research Institute, Western University, London, Canada; Department of Medical Biophysics, Western University, London, Canada
Marrissa J McIntosh Robarts Research Institute, Western University, London, Canada; Department of Medical Biophysics, Western University, London, Canada
Inderdeep Dhaliwal Division of Respirology, Department of Medicine, Western University, London, Canada
J Michael Nicholson Division of Respirology, Department of Medicine, Western University, London, Canada
Miranda Kirby Department of Physics, Toronto Metropolitan University, Toronto, Canada
Sarah Svenningsen Division of Respirology, Department of Medicine, McMaster University and Firestone Institute for Respiratory Health, St. Joseph's Health Care, Hamilton, Canada
Grace Parraga Robarts Research Institute, Western University, London, Canada; Department of Medical Biophysics, Western University, London, Canada; Division of Respirology, Department of Medicine, Western University, London, Canada.

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129Xe MRI and Oscillometry of Irritant-Induced Asthma After Bronchial Thermoplasty

Irritant-induced asthma (IIA) may develop after acute inhalational exposure in individuals without preexisting asthma. The effect of bronchial thermoplasty to treat intractable, worsening IIA has not yet been described. We evaluated a previously healthy 52-year-old man after inhalation of an unknown white powder. His pulmonary function and symptoms/quality of life worsened over 4 years, despite maximal guidelines-based asthma therapy. We acquired 129Xe MRI and pulmonary function test measurements on three occasions including before and after bronchial thermoplasty treatment. Seven months after bronchial thermoplasty, improved MRI ventilation and oscillometry small airway resistance were observed. Spirometry and asthma control did not improve until 19 months after bronchial thermoplasty, 5.5 years postexposure. Together, oscillometry measurements of the small airways and 129Xe MRI provided effort-independent, sensitive, and objective measurements of response to therapy. Improved MRI and oscillometry small airway resistance measurements temporally preceded improved airflow obstruction and may be considered for complex asthma cases.

Review of quantitative and functional lung imaging evidence of vaping-related lung injury

Introduction

The pulmonary effects of e-cigarette use (or vaping) became a healthcare concern in 2019, following the rapid increase of e-cigarette-related or vaping-associated lung injury (EVALI) in young people, which resulted in the critical care admission of thousands of teenagers and young adults. Pulmonary functional imaging is well-positioned to provide information about the acute and chronic effects of vaping. We generated a systematic review to retrieve relevant imaging studies that describe the acute and chronic imaging findings that underly vaping-related lung structure-function abnormalities.

Methods

A systematic review was undertaken on June 13th, 2023 using PubMed to search for published manuscripts using the following criteria: [("Vaping" OR "e-cigarette" OR "EVALI") AND ("MRI" OR "CT" OR "Imaging")]. We included only studies involving human participants, vaping/e-cigarette use, and MRI, CT and/or PET.

Results

The search identified 445 manuscripts, of which 110 (668 unique participants) specifically mentioned MRI, PET or CT imaging in cases or retrospective case series of patients who vaped. This included 105 manuscripts specific to CT (626 participants), three manuscripts which mainly used MRI (23 participants), and two manuscripts which described PET findings (20 participants). Most studies were conducted in North America (n = 90), with the remaining studies conducted in Europe (n = 15), Asia (n = 4) and South America (n = 1). The vast majority of publications described case studies (n = 93) and a few described larger retrospective or prospective studies (n = 17). In e-cigarette users and patients with EVALI, key CT findings included ground-glass opacities, consolidations and subpleural sparing, MRI revealed abnormal ventilation, perfusion and ventilation/perfusion matching, while PET showed evidence of pulmonary inflammation.

Discussion and conclusion

Pulmonary structural and functional imaging abnormalities were common in patients with EVALI and in e-cigarette users with or without respiratory symptoms, which suggests that functional MRI may be helpful in the investigation of the pulmonary health effects associated with e-cigarette use.

A new approach to computed tomography measurement of airway remodelling in paediatric asthma

Internal normalisation to reference structures on quantitative chest CT imaging (e.g. lung airway dimensions to adjacent vascular dimensions) provides a potential way to standardise image measurements to population characteristics https://bit.ly/3Rh9pnW.

129Xe MRI Ventilation Defects in Asthma: What is the Upper Limit of Normal and Minimal Clinically Important Difference?

RATIONALE AND OBJECTIVES

The minimal clinically important difference (MCID) and upper limit of normal (ULN) for MRI ventilation defect percent (VDP) were previously reported for hyperpolarized 3He gas MRI. Hyperpolarized 129Xe VDP is more sensitive to airway dysfunction than 3He, therefore the objective of this study was to determine the ULN and MCID for 129Xe MRI VDP in healthy and asthma participants.

MATERIALS AND METHODS

We retrospectively evaluated healthy and asthma participants who underwent spirometry and 129XeMRI on a single visit; participants with asthma completed the asthma control questionnaire (ACQ-7). The MCID was estimated using distribution- (smallest detectable difference [SDD]) and anchor-based (ACQ-7) methods. Two observers measured VDP (semiautomated k-means-cluster segmentation algorithm) in 10 participants with asthma, five-times each in random order, to determine SDD. The ULN was estimated based on the 95% confidence interval of the relationships between VDP and age.

RESULTS

Mean VDP was 1.6 ± 1.2% for healthy (n = 27) and 13.7 ± 12.9% for asthma participants (n = 55). ACQ-7 and VDP were correlated (r = .37, p = .006; VDP = 3.5·ACQ + 4.9). The anchor-based MCID was 1.75% while the mean SDD and distribution-based MCID was 2.25%. VDP was correlated with age for healthy participants (p = .56, p =.003; VDP = .04·Age-.01). The ULN for all healthy participants was 2.0%. By age tertiles, the ULN was 1.3% ages 18-39 years, 2.5% for 40-59 years and 3.8% for 60-79 years.

CONCLUSION

The 129Xe MRI VDP MCID was estimated in participants with asthma; the ULN was estimated in healthy participants across a range of ages, both of which provide a way to interpret VDP measurements in clinical investigations.

Longitudinal follow-up of postacute COVID-19 syndrome: DLCO, quality-of-life and MRI pulmonary gas-exchange abnormalities

¹²⁹Xe MRI red blood cell to alveolar tissue plasma ratio (RBC:TP) abnormalities have been observed in ever-hospitalised and never-hospitalised people with postacute COVID-19 syndrome (PACS). But, it is not known if such abnormalities resolve when symptoms and quality-of-life scores improve. We evaluated 21 participants with PACS, 7±4 months (baseline) and 14±4 months (follow-up) postinfection. Significantly improved diffusing capacity of the lung for carbon monoxide (DL_CO, Δ=14%_pred ;95%CI 7 to 21, p<0.001), postexertional dyspnoea (Δ=-0.7; 95%CI=-0.2 to -1.2, p=0.019), St George's Respiratory Questionnaire-score (SGRQ Δ=-6; 95% CI=-1 to -11, p=0.044) but not RBC:TP (Δ=0.03; 95% CI=0.01 to 0.05, p=0.051) were observed at 14 months. DL_CO correlated with RBC:TP (r=0.60, 95% CI=0.22 to 0.82, p=0.004) at 7 months. While DL_CO and SGRQ measurements improved, these values did not normalise 14 months post-infection. ClinicalTrials.gov NCT04584671.

CT Mucus Score and 129Xe MRI Ventilation Defects After 2.5 Years' Anti-IL-5Rα in Eosinophilic Asthma

BACKGROUND

We previously showed in patients with poorly controlled eosinophilic asthma that a single dose of benralizumab resulted in significantly improved asthma-control-questionnaire (ACQ-6) score and ¹²⁹Xe MRI ventilation defect percent (VDP), 28 days post-injection, and ¹²⁹Xe MRI VDP and CT airway mucus occlusions were shown to independently predict this early ACQ-6 response to benralizumab.

RESEARCH QUESTION

Do early VDP responses at 28 days persist, and do FEV₁, fractional exhaled nitric oxide (Feno), and mucus plug score improve during a 2.5 year treatment period?

STUDY DESIGN AND METHODS

Participants with poorly controlled eosinophilic asthma completed spirometry, ACQ-6, and MRI, 28 days, 1, and 2.5 years after benralizumab; chest CT was acquired at enrollment and 2.5 years later.

RESULTS

Of 29 participants evaluated at 28 days post-benralizumab, 16 participants returned for follow-up while on therapy at 1 year, and 13 participants were evaluable while on therapy at 2.5 years, post-benralizumab initiation. As compared with 28 days post-benralizumab, ACQ-6 score (2.0 ± 1.4) significantly improved after 1 year (0.5 ± 0.6, P = .02; 95% CI, 0.1-1.1) and 2.5 years (0.5 ± 0.5, P = .03; 95% CI, 0.1-1.1). The mean VDP change at 2.5 years (-4% ± 3%) was greater than the minimal clinically important difference, but not significantly different from VDP measured 28 days post-benralizumab. Mucus score (3 ± 4) was significantly improved at 2.5 years (1 ± 1, P = .03; 95% CI, 0.3-5.5). In six of eight participants with previous occlusions, mucus plugs vanished or substantially diminished 2.5 years later. VDP (P < .001) and mucus score (P < .001) measured at baseline, but not Feno or FEV₁, independently predicted ACQ score after 2.5 years.

INTERPRETATION

In poorly controlled eosinophilic asthma, early MRI VDP responses at 28 days post-benralizumab persisted 2.5 years later, alongside significantly improved mucus score and asthma control.

Post-Acute COVID-19 Syndrome: 129Xe MRI Ventilation Defects and Respiratory Outcomes One Year Later

Background In people with post-acute COVID-19 syndrome (PACS) and normal pulmonary function, ¹²⁹Xe MRI ventilation defects, abnormal quality-of-life scores, and exercise limitation were reported 3-months after infection; the longitudinal trajectory remains unclear. Purpose To measure and compare pulmonary function, exercise capacity, quality-of-life, and ¹²⁹Xe MRI ventilation defect percent (VDP) in people with PACS evaluated 3- and 15-months post-infection. Materials and Methods In this prospective study, participants with PACS aged 18-80 years were enrolled between July 2020 and August 2021 from two quaternary care centers. They were evaluated 3-months and 15-months post-infection for: ¹²⁹Xe MRI VDP, diffusing capacity of the lung for carbon monoxide (DL_CO), spirometry, oscillometry, six-minute walk distance (6MWD), and St. George's Respiratory Questionnaire (SGRQ). Differences between time-points were evaluated using paired t-tests. Multivariable models were generated to explain exercise capacity and quality-of-life improvements. Odds ratios (OR) were used to evaluate potential treatment influences. Results Fifty-three participants (mean age, 55 years ±18[SD]; 26 male; 27 female) attended both 3- and 15-month visits and were included in analysis. ¹²⁹Xe MRI VDP (5.4%, 4.2%; P=.003), forced expiratory volume in 1-second (85%_pred, 90%_pred; P=.001), DL_CO (89%_pred, 99%_pred; P=.002) and SGRQ (35, 25; P<.001) improved between the 3- and 15-month visit. VDP measured at 3- months post-COVID predicted the change in 6MWD (β=-.643, P=.001) while treatment with respiratory medication at 3-months predicted improved 15-month quality-of-life score (OR=4.0; 95%CI:1.2,13.8, P=.03). Conclusion Pulmonary function, gas-exchange, exercise capacity, quality-of-life, and ¹²⁹Xe MRI ventilation defect percent (VDP) improved in participants with post-acute COVID-19 syndrome evaluated at 15-months as compared to 3-months post-infection. VDP measured at 3-months post-infection correlated with improved exercise capacity, whilst treatment with respiratory medication was associated with improved quality-of-life score at 15-months post-infection. Clinical Trial Registration: www.clinicaltrials.gov NCT05014516 See also the editorial by Vogel-Claussen in this issue.

Pulmonary MRI and Cluster Analysis Help Identify Novel Asthma Phenotypes

BACKGROUND

Outside eosinophilia, current clinical asthma phenotypes do not show strong relationships with disease pathogenesis or treatment responses. While chest x-ray computed tomography (CT) phenotypes have previously been explored, functional MRI measurements provide complementary phenotypic information.

PURPOSE

To derive novel data-driven asthma phenotypic clusters using functional MRI airway biomarkers that better describe airway pathologies in patients.

STUDY TYPE

Retrospective.

POPULATION

A total of 45 patients with asthma who underwent post-bronchodilator ¹²⁹ Xe MRI, volume-matched CT, spirometry and plethysmography within a 90-minute visit.

FIELD STRENGTH/SEQUENCE

Three-dimensional gradient-recalled echo ¹²⁹ Xe ventilation sequence at 3 T.

ASSESSMENT

We measured MRI ventilation defect percent (VDP), CT airway wall-area percent (WA%), wall-thickness (WT, WT* [*normalized for age/sex/height]), lumen-area (LA), lumen-diameter (D, D*) and total airway count (TAC). Univariate relationships were utilized to select variables for k-means cluster analysis and phenotypic subgroup generation. Spirometry and plethysmography measurements were compared across imaging-based clusters.

STATISTICAL TESTS

Spearman correlation (ρ), one-way analysis of variance (ANOVA) or Kruskal-Wallis tests with post hoc Bonferroni correction for multiple comparisons, significance level 0.05.

RESULTS

Based on limited common variance (Kaiser-Meyer-Olkin-measure = 0.44), four unique clusters were generated using MRI VDP, TAC, WT* and D* (52 ± 14 years, 27 female). Imaging measurements were significantly different across clusters as was the forced expiratory volume in 1-second (FEV₁ %_pred ), residual volume/total lung capacity and airways resistance. Asthma-control (P = 0.9), quality-of-life scores (P = 0.7) and the proportions of severe-asthma (P = 0.4) were not significantly different. Cluster1 (n = 15/8 female) reflected mildly abnormal CT airway measurements and FEV₁ with moderately abnormal VDP. Cluster2 (n = 12/12 female) reflected moderately abnormal TAC, WT and FEV₁ . In Cluster3 and Cluster4 (n = 14/6 female, n = 4/1 female, respectively), there was severely reduced TAC, D and FEV₁ , but Cluster4 also had significantly worse, severely abnormal VDP (7 ± 5% vs. 41 ± 12%).

DATA CONCLUSION

We generated four proof-of-concept MRI-derived clusters of asthma with distinct structure-function pathologies. Cluster analysis of asthma using ¹²⁹ Xe MRI in combination with CT biomarkers is feasible and may challenge currently used paradigms for asthma phenotyping and treatment decisions.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage.

Persistent 129Xe MRI Pulmonary and CT Vascular Abnormalities in Symptomatic Individuals with Post-Acute COVID-19 Syndrome

Background In patients with post-acute COVID-19-syndrome (PACS), abnormal gas-transfer and pulmonary vascular density have been reported, but such findings have not been related to each other, or to symptoms and exercise limitation. The pathophysiological drivers of PACS in ever- and never-hospitalized patients are not well-understood. Purpose To determine the relationship of persistent symptoms and exercise limitation with ¹²⁹Xe MRI and CT pulmonary vascular measurements in individuals with PACS. Materials and Methods In this prospective study, patients with PACS aged 18-80 years with a positive PCR COVID test were recruited from a quaternary-care COVID-19 clinic between April and October 2021. Participants with PACS underwent spirometry, diffusing-capacity-of-the-lung- for-carbon-monoxide (DLco), ¹²⁹Xe MRI, and chest CT. Healthy controls had no prior history of COVID-19 underwent spirometry, DLco, and ¹²⁹Xe MRI. The ¹²⁹Xe MRI red-blood-cell (RBC) to alveolar-barrier signal ratio, RBC area-under-the-curve (AUC), CT volume-of-pulmonary-vessels with cross-sectional-area <5mm² (BV5), and total-blood-volume (TBV) were quantified. St. George's Respiratory Questionnaire (SGRQ), International Physical Activity Questionnaire (IPAQ) and modified Borg Dyspnea Scale (mBDS) measured quality-of-life, exercise limitation and dyspnea. Differences between groups were compared using Welch's T-tests or Welch's ANOVA. Relationships were evaluated using Pearson (r) and Spearman (ρ) correlations. Results Forty participants were evaluated including six controls (mean age, 35±15 years[standard deviation], 3 women) and 34 participants with PACS (mean age, 53±13 years[SD], 18 women), of which 22 were never-hospitalized. The ¹²⁹Xe MRI RBC:barrier ratio was lower in ever- hospitalized participants (P=.04) compared to controls. BV5 correlated with RBC AUC (ρ=.44,P=.03). The ¹²⁹Xe MRI RBC:barrier ratio was related to DLco (r=.57,P=.002) and FEV₁ (ρ=.35,P=.03); RBC AUC was related to dyspnea (ρ=-.35,P=.04) and IPAQ score (ρ=.45,P=.02). Conclusion ¹²⁹Xe MRI measurements were lower in ever- hospitalized participants with post- acute COVID-19-syndrome, 34±25 weeks post-infection compared to controls. ¹²⁹Xe MRI measures were associated with CT pulmonary vascular density, DLco, exercise capacity, and dyspnea. ClinicalTrials.gov: NCT04584671 See also the editorial by Wild and Collier.

129Xe MRI ventilation defects in ever-hospitalised and never-hospitalised people with post-acute COVID-19 syndrome

BACKGROUND

Patients often report persistent symptoms beyond the acute infectious phase of COVID-19. Hyperpolarised ¹²⁹Xe MRI provides a way to directly measure airway functional abnormalities; the clinical relevance of ¹²⁹Xe MRI ventilation defects in ever-hospitalised and never-hospitalised patients who had COVID-19 has not been ascertained. It remains unclear if persistent symptoms beyond the infectious phase are related to small airways disease and ventilation heterogeneity. Hence, we measured ¹²⁹Xe MRI ventilation defects, pulmonary function and symptoms in ever-hospitalised and never-hospitalised patients who had COVID-19 with persistent symptoms consistent with post-acute COVID-19 syndrome (PACS).

METHODS

Consenting participants with a confirmed diagnosis of PACS completed ¹²⁹Xe MRI, CT, spirometry, multi-breath inert-gas washout, 6-minute walk test, St. George's Respiratory Questionnaire (SGRQ), modified Medical Research Council (mMRC) dyspnoea scale, modified Borg scale and International Physical Activity Questionnaire. Consenting ever-COVID volunteers completed ¹²⁹Xe MRI and pulmonary function tests only.

RESULTS

Seventy-six post-COVID and nine never-COVID participants were evaluated. Ventilation defect per cent (VDP) was abnormal and significantly greater in ever-COVID as compared with never-COVID participants (p<0.001) and significantly greater in ever-hospitalised compared with never-hospitalised participants who had COVID-19 (p=0.048), in whom diffusing capacity of the lung for carbon-monoxide (p=0.009) and 6-minute walk distance (6MWD) (p=0.005) were also significantly different. ¹²⁹Xe MRI VDP was also related to the 6MWD (p=0.02) and post-exertional SpO₂ (p=0.002). Participants with abnormal VDP (≥4.3%) had significantly worse 6MWD (p=0.003) and post-exertional SpO₂ (p=0.03).

CONCLUSION

¹²⁹Xe MRI VDP was significantly worse in ever-hospitalised as compared with never-hospitalised participants and was related to 6MWD and exertional SpO₂ but not SGRQ or mMRC scores.

TRIAL REGISTRATION NUMBER

NCT05014516.

Pulmonary functional MRI: Detecting the structure-function pathologies that drive asthma symptoms and quality of life

Pulmonary functional MRI (PfMRI) using inhaled hyperpolarized, radiation-free gases (such as ³ He and ¹²⁹ Xe) provides a way to directly visualize inhaled gas distribution and ventilation defects (or ventilation heterogeneity) in real time with high spatial (~mm³ ) resolution. Both gases enable quantitative measurement of terminal airway morphology, while ¹²⁹ Xe uniquely enables imaging the transfer of inhaled gas across the alveolar-capillary tissue barrier to the red blood cells. In patients with asthma, PfMRI abnormalities have been shown to reflect airway smooth muscle dysfunction, airway inflammation and remodelling, luminal occlusions and airway pruning. The method is rapid (8-15 s), cost-effective (~$300/scan) and very well tolerated in patients, even in those who are very young or very ill, because unlike computed tomography (CT), positron emission tomography and single-photon emission CT, there is no ionizing radiation and the examination takes only a few seconds. However, PfMRI is not without limitations, which include the requirement of complex image analysis, specialized equipment and additional training and quality control. We provide an overview of the three main applications of hyperpolarized noble gas MRI in asthma research including: (1) inhaled gas distribution or ventilation imaging, (2) alveolar microstructure and finally (3) gas transfer into the alveolar-capillary tissue space and from the tissue barrier into red blood cells in the pulmonary microvasculature. We highlight the evidence that supports a deeper understanding of the mechanisms of asthma worsening over time and the pathologies responsible for symptoms and disease control. We conclude with a summary of approaches that have the potential for integration into clinical workflows and that may be used to guide personalized treatment planning.

Bronchial thermoplasty guided by hyperpolarised gas magnetic resonance imaging in adults with severe asthma: a 1-year pilot randomised trial

Patient-specific localisation of ventilation defects using hyperpolarised gas magnetic resonance imaging (MRI) introduces the possibility of regionally targeted bronchial thermoplasty (BT) for the treatment of severe asthma. We aimed to demonstrate that BT guided by MRI to ventilation defects reduces the number of radiofrequency activations while resulting in improved asthma quality-of-life and control scores that are non-inferior to standard BT. In a 1-year pilot randomised controlled trial, 14 patients with severe asthma who were clinically eligible to receive BT underwent hyperpolarised gas MRI to characterise ventilation defects and were randomised to MRI-guided or standard BT. End-points were improved Asthma Quality of Life Questionnaire (AQLQ) and Asthma Control Questionnaire (ACQ) scores, the proportion of AQLQ and ACQ responders and the number of radiofrequency activations and bronchoscopy sessions. Participants who underwent MRI-guided BT received 53% fewer radiofrequency activations than those who had standard BT (p=0.003). At 12 months, the mean improvement from baseline was similar between the MRI-guided group (n=5) and the standard group (n=7) for AQLQ score (MRI-guided: 1.8, 95% CI 0.1-3.5, p=0.04; standard: 0.7, 95% CI -0.9-2.3, p=0.30) (p=0.25) and ACQ-5 score (MRI-guided: -1.4, 95% CI -2.6- -0.2, p=0.03; standard: -0.7, 95% CI -1.3-0.0, p=0.04) (p=0.17). A similar proportion of participants in both groups achieved a clinically relevant improvement in AQLQ score (MRI-guided: 80%; standard: 71%) and ACQ-5 score (MRI-guided: 80%; standard: 57%). Hyperpolarised gas MRI-guided BT reduced the number of radiofrequency activations, and resulted in asthma quality of life and control improvements at 12 months that were non-inferior to standard BT.

Improved graft survival after renal transplantation in the United States, 1988 to 1996

BACKGROUND

The introduction of cyclosporine has resulted in improvement in the short-term outcome of renal transplantation, but its effect on the long-term survival of kidney transplants is not known.

METHODS

We analyzed the influence of demographic characteristics (age, sex, and race), transplant-related variables (living or cadaveric donor, panel-reactive antibody titer, extent of HLA matching, and cold-ischemia time), and post-transplantation variables (presence or absence of acute rejection, delayed graft function, and therapy with mycophenolate mofetil and tacrolimus) on graft survival for all 93,934 renal transplantations performed in the United States between 1988 and 1996. A regression analysis adjusted for these variables was used to estimate the risk of graft failure within the first year and more than one year after transplantation.

RESULTS

From 1988 to 1996, the one-year survival rate for grafts from living donors increased from 88.8 to 93.9 percent, and the rate for cadaveric grafts increased from 75.7 to 87.7 percent. The half-life for grafts from living donors increased steadily from 12.7 to 21.6 years, and that for cadaveric grafts increased from 7.9 to 13.8 years. After censoring of data for patients who died with functioning grafts, the half-life for grafts from living donors increased from 16.9 years to 35.9 years, and that for cadaveric grafts increased from 11.0 years to 19.5 years. The average yearly reduction in the relative hazard of graft failure after one year was 4.2 percent for all recipients (P<0.001), 0.4 percent for those who had acute rejection (P=0.57), and 6.3 percent for those who did not have acute rejection (P<0.001).

CONCLUSIONS

Since 1988, there has been a substantial increase in short-term and long-term survival of kidney grafts from both living and cadaveric donors.

Pharmacokinetics and tolerability of a novel 5-HT1D agonist, PNU-142633F

OBJECTIVES

The objectives of this study were to characterize the safety, tolerability and pharmacokinetics of a single, oral dose of PNU-142633F escalating over the range of 1.0 mg to 100 mg (free base equivalents).

METHODS

This was a randomized, double-blind, single-dose, placebo-controlled, dose-escalation trial, with each dose group (1.0, 3.0, 10, 30, 50, 75 and 100 mg) having eight volunteers (six PNU-142633F and two placebo). Clinical laboratory tests, electrocardiogram, Holter monitoring, and assessment of adverse events were used to gauge the tolerability of PNU-142633. Serial blood samples and urine collections were obtained and plasma and urine PNU-142633 concentrations were determined by a validated HPLC fluorescence method.

RESULTS

PNU-142633 was well tolerated after oral administration. There were no reports of serious or unexpected adverse events. The most common adverse event that was possibly medication-related was transient dizziness. There were no clinically significant or dose-related effects of PNU-142633 on any vital sign parameters (aural temperature, systolic and diastolic blood pressure, pulse rate or respiratory rate), at any study time or dose. There were no clinically significant ECG changes. Only sporadic abnormalities in clinical chemistry values and hematology were noted. After the 1.0 mg and 3.0 mg doses, plasma concentrations of PNU-142633 were either below or only slightly above the lower limit of quantitation (2 ng/ml). At higher doses (30-100 mg) the terminal half-life was relatively constant at approximately 11 hours. Neither Cmax nor AUC(0-infinity) increased proportionally with the administered dose. The mean percentage of the dose excreted in the urine as intact PNU-142633 increased from 14.3% after the 1 mg dose to 49.3% after the 100 mg dose.

CONCLUSIONS

The clinical safety and pharmacokinetic data support the study of this agent as a potential treatment for migraine attacks.

A meta-analysis of fibromyalgia treatment interventions

OBJECTIVE

To evaluate and compare the efficacy of pharmacological and nonpharmacological treatments of fibromyalgia syndrome (FMS).

METHODS

This meta-analysis of 49 fibromyalgia treatment outcome studies assessed the efficacy of pharmacological and nonpharmacological treatment across four types of outcome measures-physical status, self-report of FMS symptoms, psychological status, and daily functioning.

RESULTS

After controlling for study design, antidepressants resulted in improvements on physical status and self-report of FMS symptoms. All nonpharmacological treatments were associated with significant improvements in all four categories of outcome measures with the exception that physically-based treatment (primarily exercise) did not significantly improve daily functioning. When compared, nonpharmacological treatment appears to be more efficacious in improving self-report of FMS symptoms than pharmacological treatment alone. A similar trend was suggested for functional measures.

CONCLUSION

The optimal intervention for FMS would include nonpharmacological treatments, specifically exercise and cognitive-behavioral therapy, in addition to appropriate medication management as needed for sleep and pain symptoms.

Protocol for verifying expertise in locating fibromyalgia tender points

OBJECTIVE

To develop a protocol for determining when an individual is adequately trained to locate the tender points relative to fibromyalgia in an exam.

METHODS

The error distance for each tender point was established by polling individuals with experience in conducting tender point exams. Bayesian statistical methods were employed to form a protocol for determining an individual's proficiency in locating the tender points. A predictive distribution was utilized to find the probability of remaining trained at locating tender points. Also, the probability of classifying at least 11 tender points as tender (mild) under different "locating" criteria and different number of points that are truly tender was computed.

RESULTS

Critical values indicating the number of tender points needed in the qualification process for various standards of reliability--80%, 85%, and 90%--are presented. To be certified after 3 subjects have been examined in the 80%, 85%, and 90% criteria, one has to correctly identify 48, 50, and 52, respectively, out of the 54 possible tender points.

CONCLUSION

We believe that at least 3 subjects should be examined before certification is granted using any of the 3 criteria--80%, 85%, and 90%. In our example, when using the 85% criterion, the qualification process required 7 subjects to certify an individual.

Biofeedback/relaxation training and exercise interventions for fibromyalgia: a prospective trial

OBJECTIVE

To compare the effectiveness of biofeedback/relaxation, exercise, and a combined program for the treatment of fibromyalgia.

METHODS

Subjects (n = 119) were randomly assigned to one of 4 groups: 1) biofeedback/relaxation training, 2) exercise training, 3) a combination treatment, or 4) an educational/attention control program.

RESULTS

All 3 treatment groups produced improvements in self-efficacy for function relative to the control condition. In addition, all treatment groups were significantly different from the control group on tender point index scores, reflecting a modest deterioration by the attention control group rather than improvements by the treatment groups. The exercise and combination groups also resulted in modest improvements on a physical activity measure. The combination group best maintained benefits across the 2-year period.

CONCLUSION

This study demonstrates that these 3 treatment interventions result in improved self-efficacy for physical function which was best maintained by the combination group.

Action of lead on neurotransmission in rats

1. The neurotoxic effect of lead on the catecholaminergic and cholinergic nervous systems has been investigated using a rat model of lead exposure. 2. This model of lead exposure resulted in significant quantities of lead accumulating in the blood, brain and femur of the lead-exposed animals. 3. The biochemical effect of lead on brain neurochemistry was dependent on the degree and duration of lead exposure. However, the data points to a selective action of lead, with the midbrain and diencephalon being prime targets while very few lead-related alterations were observed in the cerebellum or the telencephalon. 4. Within the catecholaminergic nervous system, lead exposure resulted in alterations in the concentrations of the transmitters, noradrenaline and dopamine, in addition to changes in the activities of the enzymes tyrosine hydroxylase and phenylethanolamine-N-methyl transferase. The activity of the cholinergic biosynthetic enzyme, choline acetyltransferase was also noted to be altered by lead exposure.

Effects of lead exposure on rat brain catecholaminergic neurochemistry

1. The effects of lead on catecholaminergic neurotransmission have been investigated. 2. Using the rat as a model, animals were exposed both acutely and chronically to lead. The levels of catecholamines, noradrenaline, adrenaline, and dopamine along with the activities of tyrosine hydroxylase and phenylethanolamine-N-methyl transferase were measured in 5 brain regions--cerebral cortex, brainstem, hippocampus, anterior and posterior hypothalamus. 3. A lead related reduction in the activity of tyrosine hydroxylase was observed in association with alterations in steady-state levels of the catecholamines in the posterior and anterior hypothalamus. 4. Thus, lead exposure, known to result in behavioural changes, is associated with localised neurochemical effects on the hypothalamus.

Influence of lead exposure on catecholamine metabolism in discrete rat brain nuclei

1. Using the rat exposed both acutely and chronically to lead as a model of lead neurotoxicity, various parameters of catecholamine metabolism were investigated. 2. The steady-state concentrations of noradrenaline, adrenaline and dopamine together with the activities of tyrosine hydroxylase and phenylethanolamine N-methyl transferase were measured in discrete brain nuclei--periventricular, paraventricular, median eminence, posterior and anterior hypothalamus, caudate putamen and globus pallidus. 3. Lead exposure resulted in significant fall in the activity of the rate-limiting enzyme of catecholamine synthesis, tyrosine hydroxylase which was associated with alterations in concentrations of catecholamines in the median eminence, periventricular nucleus and anterior hypothalamus. 4. No other brain nuclei investigated exhibited any effect of lead on the catecholaminergic nervous system and, therefore, the effect of lead on rat brain can be considered to be regionally specific.

An isolated upper airway preparation in conscious dogs

The purpose of this study was to develop an isolated upper airway preparation in conscious dogs. Each of the four dogs was trained to wear an individually fitted respiratory mask and surgically prepared with two side-hole tracheostomies. After full recovery, one endotracheal tube was inserted caudally into the lower tracheostomy hole and another tube cranially into the upper tracheostomy. When the two endotracheal tubes were connected to a breathing circuit including a box-balloon system, the magnitude and pattern of the inspiratory flow through the upper airway were identical to that inhaled spontaneously into the lungs by the dogs, but the gas medium inhaled into the upper airway could be independently controlled. Thus it allowed test gas mixtures to be inhaled spontaneously through an isolated upper airway. One limitation was that the inspired gas remained in the upper airway during expiration, but this can be corrected by a simple modification of the breathing circuit. This preparation was tested in studying the respiratory effects of upper airway exposure to CO2 gas mixtures. Our results showed small but significant reduction in both rate and volume of respiration when the concentration of CO2 gas mixture inhaled through the upper airway exceeded 5%. Irregular breathing patterns were frequently elicited in these dogs by higher concentrations (greater than 12%) of CO2.

The neurotoxicology of lead

In the past six years, our research group has investigated the relationship between lead exposure and mental and behavioural development. This has been carried out through studies in children and animals. Earlier studies in children have shown that associations might be expected between environmental exposure to lead and various aspects of cognitive and behavioural development. Our study has examined and continues to examine, a cohort of children sub-divided into three groups according to the level of lead exposure during early 'in utero' development. Data amassed to date includes measurement of psychometric function and post natal development, together with biochemical measures of lead exposure. Assessment will continue through to early scholastic performance and will include measurement of deciduous tooth lead concentration as an integrated measure of long term exposure. In addition to these studies in children, a series of neurochemical studies have been carried out using a rat model of lead exposure. Data obtained from both our own neurochemical experiments and those of other groups indicate an extremely complex plethora of neurotoxic actions of lead.

Neurotoxic action of lead: effect on tetrahydrobiopterin metabolism in the rat

The effects of lead, a known neurotoxin on the metabolism of a vital tetrahydrobiopterin cofactor for the hydroxylation enzymes tyrosine hydroxylase, phenylalanine hydroxylase and tryptophan hydroxylase, have been investigated. Reduced availability of this pteridine has the potential to reduce the level of the neurotransmitters noradrenaline, adrenaline and 5-hydroxytryptophan in the brain. Using the rat as a model, increases in tetrahydrobiopterin concentration and in the activity of dihydropteridine reductase, an enzyme involved in tetrahydrobiopterin metabolism, were observed after exposure to lead via the drinking water. Possible explanations for this increased level of tetrahydrobiopterin relate to alterations in the balance between synthesis and salvage of this co-factor.

Studies of lead and cadmium exposure in Glasgow, U.K

Domestic water and whole blood samples were collected early in 1981 from two hundred volunteers living in the Glasgow area of Scotland, U.K. The concentration of lead in the water and blood samples, and of cadmium in the blood, was measured. The blood lead and cadmium concentrations were compared to those obtained in the Survey of 1979. There has been a fall in blood lead concentrations since the 1979 Survey. In contrast, the blood cadmium levels had remained similar. This diminution in blood lead concentration is attributed to a fall in water lead concentration caused by raising the pH of the water supply in the Glasgow area. The main determinant for cadmium in blood appears to be cigarette smoking habits, which had not changed.