United States

Background
Obstructive sleep apnea (OSA) is a breathing disorder characterized by recurrent relaxation of the tongue and soft palate during sleep. The genioglossus (GG) muscle, the largest extrinsic tongue muscle, maintains upper airway patency. Obesity-induced OSA decreases muscular tone in the GG, causing airway obstruction. Other muscles impacted by obesity, such as the diaphragm (DIA) and the sternocleidomastoid, may contribute to OSA complications. Leptin partakes in central regulation of upper airway patency and diaphragmatic control. Leptin-
deficient obese (ob/ob) mice exhibit pharyngeal collapsibility and provide an effective model of OSA effects. By using ob/ob mice, we study the impact of obesity on GG, DIA, and sternomastoid (ST) muscles with a focus on the neuromuscular junction (NMJ), the best indicator of muscle function. 

Methods
GG, ST, and DIA muscles were extracted from 16 and 20-week wild-type (WT) and ob/ob male and female mice. Some samples were fixed and incubated with Alexa594TM alpha-bungarotoxin to visualize nicotinic acetylcholine receptors (nAChRs), and Alexa488TM Cholera toxin to label lipid rafts. They were imaged with a NikonTM inverted fluorescence microscope and a Confocal Microscope. Other GG and ST samples were “snap frozen,” sectioned in a cryostat, and stained
with H&amp;E and NADH.

Results
GG muscles of ob/ob male mice showed a significant decrease in postsynaptic nAChRs and lipid rafts density compared to age-matched controls. In contrast to WT, GG of ob/ob male mice displayed multiply-innervated NMJs, nerve sprouting, and multiple Schwann cells engulfing nerves. Furthermore, the GG of ob/ob males exhibited central nuclei, intermuscular fat deposition, and hypertrophy. ST muscles in 16-week male WT and ob/ob mice displayed no differences in nAChR density, but nAChR density decreased in 20-week ob/ob male mice. The DIA showed higher nAChR density in ob/ob mice compared to controls. Female WT and ob/ob
mice showed insignificant changes in nAChR density in GG, ST, and Dia. 

Conclusion
The reduction in postsynaptic nAChRs and lipid rafts densities, and presynaptic remodeling of NMJs of GG observed in male ob/ob mice suggest synaptic disassembly. NMJ dismantlement, not observed in female ob/ob mice, may suggest female sex hormones contribute to synapse preservation through a neuroprotective pathway. Central nuclei in the GG indicate hypertrophic regeneration. Increased nAChR density in the male ob/ob DIA suggests a compensatory mechanism. Therefore, obesity-induced OSA-associated pathology exclusive to male GG, ST, and DIA affects the synaptic strength of these muscles. The observed sexual dimorphism and the possibility of reversing these observed changes should be further explored.

AMA Research Challenge 2023

Effects of Obesity on the Neuromuscular Junction of Genioglossus Muscle and Other Associated Muscles of Respiration

Background
Obstructive sleep apnea (OSA) is a breathing disorder characterized by recurrent relaxation of the tongue and soft palate during sleep. The genioglossus (GG) muscle, the largest extrinsic tongue muscle, maintains upper airway patency. Obesity-induced OSA decreases muscular tone in the GG, causing airway obstruction. Other muscles impacted by obesity, such as the diaphragm (DIA) and the sternocleidomastoid, may contribute to OSA complications. Leptin partakes in central regulation of upper airway patency and diaphragmatic control. Leptin-
deficient obese (ob/ob) mice exhibit pharyngeal collapsibility and provide an effective model of OSA effects. By using ob/ob mice, we study the impact of obesity on GG, DIA, and sternomastoid (ST) muscles with a focus on the neuromuscular junction (NMJ), the best indicator of muscle function. 

Methods
GG, ST, and DIA muscles were extracted from 16 and 20-week wild-type (WT) and ob/ob male and female mice. Some samples were fixed and incubated with Alexa594TM alpha-bungarotoxin to visualize nicotinic acetylcholine receptors (nAChRs), and Alexa488TM Cholera toxin to label lipid rafts. They were imaged with a NikonTM inverted fluorescence microscope and a Confocal Microscope. Other GG and ST samples were “snap frozen,” sectioned in a cryostat, and stained
with H&E and NADH.

Results
GG muscles of ob/ob male mice showed a significant decrease in postsynaptic nAChRs and lipid rafts density compared to age-matched controls. In contrast to WT, GG of ob/ob male mice displayed multiply-innervated NMJs, nerve sprouting, and multiple Schwann cells engulfing nerves. Furthermore, the GG of ob/ob males exhibited central nuclei, intermuscular fat deposition, and hypertrophy. ST muscles in 16-week male WT and ob/ob mice displayed no differences in nAChR density, but nAChR density decreased in 20-week ob/ob male mice. The DIA showed higher nAChR density in ob/ob mice compared to controls. Female WT and ob/ob
mice showed insignificant changes in nAChR density in GG, ST, and Dia. 

Conclusion
The reduction in postsynaptic nAChRs and lipid rafts densities, and presynaptic remodeling of NMJs of GG observed in male ob/ob mice suggest synaptic disassembly. NMJ dismantlement, not observed in female ob/ob mice, may suggest female sex hormones contribute to synapse preservation through a neuroprotective pathway. Central nuclei in the GG indicate hypertrophic regeneration. Increased nAChR density in the male ob/ob DIA suggests a compensatory mechanism. Therefore, obesity-induced OSA-associated pathology exclusive to male GG, ST, and DIA affects the synaptic strength of these muscles. The observed sexual dimorphism and the possibility of reversing these observed changes should be further explored.

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Background: Research shows that increased severity of congenital heart disease (CHD) is associated with increased frequency of neurological deficits in children with structural cardiac abnormalities. Young children with more complex CHDs who require cardiopulmonary bypass (CPB) have a significantly higher incidence of developmental abnormalities and neurological deficits, including academic difficulties and behavioral abnormalities. Microglia, the resident immune cells in the central nervous system, play a key role in neural immune function. Mesenchymal stromal cells (MSCs) are multipotent, non-hematopoietic cells that possess immunomodulatory and regenerative properties and regulate microglia activation. It is hypothesized that intra-arterial MSC delivery through CPB in a survival porcine model is neuroprotective by modulating systemic and brain-specific inflammatory responses.

Methods: To mimic the effects in young CHD patients, two-week old female piglets were randomly assigned to one of three treatment groups: control, CPB, and CPB+MSC. The CPB+MSC group consisted of a CPB surgery followed by MSC administration before weaning. Microglia undergo morphological changes from a naïve, ramified to an amoeboid shape under activated condition. To analyze the effects of MSCs on microglia activation, changes in the length of microglial processes and number of branch points from the nuclei were assessed.

Results: Four weeks post-surgery, analysis using Imaris software showed that CPB reduced both the length of processes and number of branch points compared to control in three different cortex regions. CPB+MSC revealed significantly longer processes (p=0.0281) and more branch points (p=0.0232) than CPB alone, indicating that morphological changes in microglia were normalized after MSC delivery.

Conclusion: MSCs regulate microglial activation and participate in the phenotypic switch from a pro-inflammatory state to a repair-permissive state. In contrast to their ramified morphology under normal conditions, activated microglia undergo structural remodeling and adopt an amoeboid morphology with highly retracted processes, a hallmark of brain inflammation, as shown in the CPB group. Microglia routinely migrate toward sites of neuronal degeneration induced by excitotoxic injury. In MSC-treated animals, there are significantly fewer amoeboid microglia with an associated increase in the length of processes and number of branch points to mitigate the effects of CPB, indicating attenuated activation of the microglia. MSC delivery during CPB is highly effective and shows translational potential to minimize CPB-induced systemic inflammation and microglial activation in children with CHD.

Effect of mesenchymal stromal cell delivery through cardiopulmonary bypass in a piglet model

Background:
Since the release of the COVID-19 vaccines, vaccine safety and hesitancy have been significant topics of contention. While studies have described COVID-19 vaccine receptiveness in the general population, its uptake in inflammatory bowel disease (IBD) patients is not well-characterized. This study aimed to investigate COVID-19 immunization rates and barriers to immunization in IBD patients.

Methods:
A retrospective study investigated 545 adult patients with Crohn’s disease (CD) or ulcerative colitis (UC) seen at an IBD subspecialty clinic at a university-based tertiary care center between January 1, 2020 and October 31, 2021. For each patient, data collected includes: demographics, past medical history, use of immunosuppressive medications, and COVID-19 and influenza immunization status. COVID-19 immunization rates in the general U.S. population were obtained from data published by the Center for Disease Control and Prevention (CDC).

Results:
As of October 31, 2021, 87.7% of IBD patients had received at least one dose of the COVID-19 vaccine, 84.4% had received the full vaccine series, and 21.8% had received the booster and/or additional dose. COVID-19 immunization rates in IBD patients were significantly higher than in the general population (p < 0.001). No significant difference was found in COVID-19 immunization rates when stratified by IBD type (CD vs UC), sex, or concurrent immunosuppressive therapy. Patients who received the COVID-19 booster/additional dose were older (mean age = 54.0 ± 17.9) than those who did not (mean age = 50.0 ± 16.5; p = 0.02). Asthmatic patients had a significantly lower rate of receiving one dose (79.5% vs 89.2%, p = 0.02) or the full series (74.7% vs 86.1%, p = 0.01) of the COVID-19 vaccine compared to non-asthmatics. Tobacco users had a significantly lower rate of receiving the full COVID-19 vaccine series (73.9% vs 85.9%, p = 0.02). Patients previously immunized for influenza had a significantly higher rate of receiving the COVID-19 booster/additional dose than those who had not (31.5% vs 17.6%, p < 0.001). History of hypertension, hyperlipidemia, heart failure, diabetes, malignancy, ischemic heart disease, pulmonary circulation disorder, or COPD did not significantly affect COVID-19 immunization rates.

Conclusion:
Our study reveals that IBD patients are more receptive to the COVID-19 vaccine compared to the general U.S. population. Immunosuppressive therapy did not affect IBD patients’ uptake of the COVID-19 vaccine, although younger age, asthma, and tobacco use were associated with decreased uptake. Particular attention is required when counseling IBD patients to identify barriers to vaccination and increase COVID-19 immunization rates.

Uptake of COVID-19 Immunization in the Inflammatory Bowel Disease Population

Background
Acute appendicitis is one of the most common surgical emergencies in the world.
Appendectomies, especially if delayed, can be associated with postoperative complications in up to 16% of the patients. Low serum albumin often indicates malnutrition or systemic inflammatory response. Past studies have demonstrated that a low albumin level, defined as less than 3.5 mg/dl, is associated with greater risks of adverse outcomes following various types of surgery, such as orthopedic or urogenital surgeries. However, limited research has specifically investigated the relationship between serum albumin levels and appendectomy outcomes. This study aimed to investigate the independent association between preoperative serum albumin levels and the likelihood of postoperative complications in adult patients undergoing appendectomy for appendicitis.

Methods
A retrospective cohort study was conducted using the National Surgical Quality Improvement Program (NSQIP) database, including adult appendectomy patients with preoperative serum albumin data and postoperative appendicitis diagnosis. Exclusion criteria included ventilator dependency, ascites, disseminated cancer, open wounds, steroid or immunosuppressant use, bleeding disorders, preoperative transfusions, moribund status, or concurrent procedures. Baseline characteristics of the patients were analyzed to identify potential confounding factors. The strength of the association between low albumin levels and postoperative complications was assessed. A multivariate logistic regression model was constructed to control for potential confounding factors.

Results
A total of 28,051 patients were included in our statistical analysis. Among them, 1,312 (4.68%) had low levels of albumin (< 3.5 g/dl), and 2,022 (7.56%) suffered from postoperative complications. This study revealed that patients with low albumin levels had significantly higher odds of postoperative complications (OR: 3.14, 95% CI: 2.70-3.64). Even after adjusting for potential confounders, including age, sex, BMI, diabetes, dyspnea, COPD, hypertension, ASA classification, sepsis status, and surgery type, patients with low albumin levels still had significantly higher odds of postoperative complications (OR: 2.22, 95% CI: 1.88-2.62). Furthermore, older age, male sex, higher ASA classification, and nonlaparoscopic appendectomy were also independently associated with greater odds of postoperative complications (all p < 0.05).

Conclusion
This study highlights a significant association between low preoperative albumin levels and an increased likelihood of post-appendectomy complications, even after accounting for other known risk factors. Low albumin levels can serve as an important indicator of nutritional status, liver or kidney disease, or ongoing inflammatory processes. Physicians can use this prognostic tool to predict adverse postoperative complications and potentially implement proactive measures to prevent or mitigate these complications, leading to improved patient outcomes.

Association Between Preoperative Serum Albumin and Risk of Complications After Appendectomy

Spalt-Like Transcription Factor 4 (SALL4), a member of the SALL family, is a regulator of embryonic stem cell development that plays a crucial role in cell renewal and proliferation. SALL4 expression is normally repressed in most adult organs but is reactivated in a multitude of solid and blood cancers and upon treatment with hypomethylating agents (HMA). There is outstanding clinical need for the development and validation of a less invasive SALL4 expression assay via peripheral blood, which can be used for monitoring patients on HMA treatment and SALL4-targeting therapy such as molecular glue degraders.

Using the Simoa (Single Molecule Array) platform, a bead-based digital enzyme-linked immunosorbent assay, we cross-tested 5 commercial SALL4 antibodies and 13 antibody pair combinations, using the best antibody pair to test the matrix effects of human plasma, buffy coats, and bone marrow aspirates. Quantitative assay development further included creating recombinant protein standards, antibody pair screening and validation, and pre-analytical optimization. Upon completion of these steps, a retrospective cohort analysis via patient peripheral blood samples is currently being conducted to validate assay accuracy and precision. Additionally, we are aiming to conduct prospective studies to explore the role of the SALL4 protein biomarker in risk stratification and treatment monitoring.

Thus far, for quantitative assay development, we have successfully expressed and purified full-length SALL4 which will be used to calibrate the standard curve and determine the assay’s limit of quantification. We also optimized multiple pre-analytic steps, including our cell lysis protocol, isolation of buffy coats using density gradient separation, and sample collection method comparison. The best antibody pair can detect both SALL4A and SALL4B isoforms, with stronger signal detected with the SALL4A isoform. For the retrospective cohort validation, we have obtained samples for analysis for liver cancer, myelodysplastic syndrome (MDS), and acute myeloid leukemia (AML) with plans to expand to breast cancer and lung cancer.

In conclusion, we have developed an ultrasensitive SALL4 protein expression diagnostic assay for use in monitoring patient treatment response and for guiding targeted therapy by analyzing peripheral blood for both solid and liquid tumors. Future steps include validating the diagnostic assay for specificity and sensitivity in a retrospective cohort analysis and conducting prospective studies to explore the role of the SALL4 protein biomarker for risk stratification, monitoring on HMA treatment, and guiding targeted therapy.

Ultrasensitive detection of SALL4 oncoproteins for the use in therapeutic monitoring

Background
Links between cancer and microbes date back four millennia (Sepich-Poore et al. 2021. Science). Recently, we showed that microbial DNA is detectable in tumor tissues and patient blood from dozens of human cancer types (Poore et al. 2020. Nature; Narunsky-Haziza et al. 2022. Cell), suggesting that cell-free microbial DNA (cf-mbDNA) could augment human-centric liquid biopsies of cancer, which currently lack sensitivity at early-stage disease. Thus, we set out to build and evaluate the first multi-omic, multi-species (human+microbe) blood tests for early-stage lung cancer detection with two intended use populations: screening-eligible individuals without known disease (i.e., a “rule-in” test with high specificity), and lung nodule-bearing individuals (i.e., a “rule-out” test with high sensitivity).

Methods
We created a cancer-specific, microbial reference database using ¬de novo metagenome assembly on non-human DNA from 5187 whole-genome sequenced blood and tumor tissue samples. This microbial database was bioinformatically evaluated across 18,782 samples and ten international cohorts, with predictions made using machine learning. Diagnostic performance was measured with and without the addition of human analytes to test for synergy. Source tracking was performed among paired lung tumors, pre-operative plasma, and post-operative plasma to identify what proportion of cf-mbDNA was tumor derived. After tuning the tests using discovery cohort samples, we applied them to validation cohorts comprising (i) screening-eligible individuals without known disease and (ii) lung nodule-bearing individuals.

Results
Microbial DNA discriminated blood samples from 24 cancer types simultaneously with an average pairwise area under the receiver operating characteristic (AUROC) curve of 95.5%. A median of 81.4% of cf-mbDNA was directly attributable to intratumoral microbial DNA via source tracking, indicating its predominant tumor origin. The addition of human cell-free tumor DNA (ctDNA) fragments and two plasma-derived proteins (CEA, osteopontin (OPN)) to cf-mbDNA significantly and synergistically improved diagnostic performance (Delong’s test: p<0.001). Application of the joint host+microbial test to screening-eligible, stage I lung cancers versus healthy smokers showed a sensitivity of 68.2% at 96.2% specificity. Then, collectively across two independent validation cohorts comprising lung nodule-positive individuals, the test significantly outperformed PET-CT and clinical risk scores, with an overall specificity of 49.5% at 95.7% sensitivity.

Conclusion
A multi-omic, multi-species test diagnoses early-stage lung cancer better than existing methods. In January 2023, the FDA provided Breakthrough Designation status for this approach to determine malignancy likelihood of lung nodules for patients who refuse or lack access to PET-CT testing.

Early-stage detection of lung cancer using a multi-omic, multi-species test

Background
Digital microscopy is becoming increasingly popular in the fields of pathological education, tissue-based research, and clinical diagnosis, offering many advantages over light microscopy. With technological advancements and the ease of proliferation of reads across digital methods, pathologists now can view slides across different centers in real time, which allows for a plethora of new modalities of treatment that were not available before due to the limitations of handling slides, such as teleconsultation, quality assurance, and collaborative efforts. The aim of this study was to compare digital versus light microscopy in kidney transplant biopsies at independent sites in the context of a large, multi-center clinical trial [Clinical Trials in Organ Transplantation (CTOT-08) NCT01289717]. 
Methods
The primary objective of this pilot study is to compare digital versus light microscopy in diagnostic kidney transplant biopsies across multiple centers to validate its use in multi-center clinical trials. To achieve this objective, we aim to quantify the level of intra-rater variability by comparing the same reads (cases) across various diagnoses from pathologists at multiple sites between microscopy platforms (digital vs. light). A secondary aim is to evaluate the extent of inter-rater variability, regardless of the platform. For 32 randomly chosen transplant kidney biopsies, glass slides and corresponding digital images were assessed by 3 pathologists in a blinded and randomized fashion. The glass slides were scanned as high-resolution images and viewed with computer software. 
Results
Pathology reads from digital microscopy were comparable to light microscopy with respect to overall diagnosis and individually quantified Banff 2007 criteria. Our analysis revealed no significant differences within raters (intra-rater variability) between the two platforms for the primary diagnoses of acute cellular rejection (ACR) (p=0.646 light vs. digital), interstitial fibrosis and tubular atrophy (i.e., “chronic Injury”) (p=0.317) or borderline ACR (p=0.805) In contrast, the pairwise kappa statistics among raters revealed lower levels of agreement for borderline rejections and chronic injury when compared to acute cellular rejection.
Conclusion
Digital microscopy of kidney allograft biopsies is reliable and comparable to traditional light microscopy. The use of digital microscopy enables improved collaboration and allows for central or duplicate reading of kidney transplant biopsies in the context of a large, multi-center clinical trial. This pilot study confirmed the reliability of digital microscopy when compared to standard light microscopy but showed a low level of agreement among pathologists for some diagnoses, stressing the importance of refined criteria and alternative methods to enhance diagnostic accuracy.




Digital versus light microscopy in kidney transplant biopsies: A multicenter evaluation comparison pilot study

Introduction

Adverse outcomes and complications relating to SARS-CoV-2 (COVID-19) infection may be influenced by a number of factors, including pre-existing comorbidities and past medical history. Despite traumatic brain injury (TBI) being a public health crisis worldwide, the relationship between the prevalence of a recent TBI and adverse outcomes following COVID-19 infection remains poorly understood. This study aims to identify whether patients with a recent TBI face increased risk of mortality and adverse outcomes associated with COVID-19, as compared to patients without a recent TBI.

Methods

We queried the TriNetX United States Collaborative Network and identified patients with a recent TBI within 1 year of a hospital encounter for COVID-19. A propensity-match analysis was performed using baseline demographics and past medical history to compare patients with a recent TBI and COVID-19 to a cohort of patients with COVID-19 without recent TBI. We collected outcome measures within 1 month of COVID-19 diagnosis relating to overall mortality, intensive care unit (ICU) admission, and in-hospital complications. A Kaplan-Meier survival (KMS) analysis was performed to determine overall survival differences.

Results
A total of 13,970 patients were identified in each cohort. The mean age was 59 years old, and over 51% of patients were male. Compared to patients without a recent TBI, patients with a recent TBI had increased risk of hospitalization (OR 3.7 [95%-CI 3.5-4.0]; p<0.001), intubation (OR 2.4 [95%-CI 1.9-3.0]; p<0.001), ICU admission (OR 3.7 [95%-CI 3.3-4.0]; p<0.001), respiratory failure (OR 1.5 [95%-CI 1.4-1.6]; p<0.001), hepatic injury (OR 1.7 [95%-CI 1.3-2.3]; p=0.001), and overall mortality (OR 2.5 [95%-CI 2.2-2.8]; p<0.001) within 1 month of COVID-19 diagnosis. Recent TBI patients had reduced risk of cardiac injury (OR 0.8 [95%-CI 0.7-0.9]; p<0.001). KMS analysis demonstrates that patients with prior TBI had increased mortality within 1 month of COVID-19 diagnosis (HR 2.5 [95%-CI 2.2-2.9]; p<0.001).

Conclusion 

Patients with recent TBI up to 12 months prior to a separate hospital encounter for COVID-19 diagnosis have increased risk of hospitalization, intubation, ICU admission, respiratory failure, hepatic injury, and overall mortality within 1 month of COVID-19 diagnosis. We hope that these results improve medical decision-making and management of patients with a recent TBI and COVID-19.

The Impact of a Traumatic Brain Injury Within 1 Year of COVID-19 Infection: A Propensity-Match Analysis

Glioblastoma Multiforme (GBM) is one of the most common and aggressive high-grade primary brain tumors that arises from the glial cells of the central nervous system and occurs most often in the frontal and temporal lobes. Despite current treatment options, long-term prognosis of GBM remains low with no significant improvement rates. Chimeric antigen receptor (CAR)-expressing T cells target the B cell marker CD19 and have shown increased efficacy in B cell lymphomas, and lymphoblastic leukemias suggesting benefits in GBM. This study aims to quantify the persistence of CAR-T cells in the context of GBM tumor volume following neurosurgical debulking procedure. A radiology software known as the mint Lesion was utilized to provide Tumor Response Assessment by Criteria (TRAC) reports that consist of volumetric measurements of the tumor lesions (target enhancing lesions, non-target enhancing lesions, and non-target non-enhancing lesions). Fluorescence-activated cell sorting (FACS) analysis takes a sample mixture of cells and sorts them into different populations based on specific biomarkers and characteristics. B7-H3 CAR-T cell persistence was increased in patients with a larger post-surgical tumor volume (3.04% Subject 001 with 2438 mm² volume and 2.38% Subject 003 with 224 mm² tumor volume). However, the number of CAR-T cells per 1 mm² was significantly reduced in patients with a larger post-surgical tumor volume (0.0012 cells/mm² Subject 001 and 0.010 cells/mm² Subject 003). This study shows that although there is an overall increased CAR-T cell persistence for a larger tumor volume, the number of CAR-T cells per 1 mm² is significantly smaller for larger tumor volumes, while illustrating that a larger post-surgical tumor bulk volume is correlated with an increased CAR-T cell persistence within 1-week post-infusion. These findings provide novel information and complement other correlative studies as part of the Phase 1 interventional clinical trial for glioblastoma patients.

Glioblastoma Multiforme Tumor Volume and Persistence of Chimeric Antigen Receptor T Cells Following Neurosurgical Debulking

Background
Healthcare disparity is the United States has been a long-standing issue. A disease of interest is diabetic retinopathy, one of the leading causes of blindness in the United States, as the minorities are disproportionately affected. Treatment regimens often consist of panretinal photocoagulation (PRP) and intravitreal injections (IVI) with anti-vascular endothelial growth factor (anti-VEGF). However, the efficacy of the treatment regimens as demonstrated in clinical trials have been limited in real-world settings as these necessitate frequent follow-ups, a challenge given that 25 to 51% of patients with diabetic retinopathy are lost to follow-ups. Furthermore, the effect of LTFU in itself on final outcomes have not been studied to date. Therefore, we examined factors associated with LTFU, the effect of LTFU on proliferative diabetic retinopathy, and its interaction with different treatments.

Methods
A retrospective cohort study at a large safety net hospital examined 271 eyes of 271 patients with PDR that received PRP or IVI over a 2-year period. LTFU was defined as failure to return to care for at least 6 months. Baseline patient characteristics were collected. Ocular data was gathered at the visit before being LTFU, the return visit after being LTFU, and the final clinic visit. Univariate analyses and multivariate regression with adjustment for multiple comparisons to control confounders were conducted. 

Results
A history of LTFU was associated with subsequent neovascularization elsewhere (NVE) and tractional retinal detachment (TRD) but not with final visual acuity (VA). Among those LTFU, those who received IVI were not at higher risk of TRD than those receiving PRP.

Conclusion
Undergoing PRP is associated with LTFU. LTFU is independently associated with subsequent development of NVE and TRD, but not with the final visual acuity. One rationale in opting for PRP over IVI for managing PDR was the risk of the patient being LTFU, but our study did not demonstrate a difference between those who received PRP prior to LTFU and those who received IVI prior to LTFU in terms of the rate of subsequent TRD formation. Further studies should expand upon those findings to design better interventions strategies. 


Out of Sight, Not Out of Mind: The Effect of Loss to Follow-Up on on Proliferative Diabetic Retinopathy

Introduction: 
Current AAOS guidelines recommend that children younger than thirty-six months with a femur fracture be evaluated for non-accidental trauma. However, the likelihood of abuse in walking-age children presenting with these fractures has been found to be less than 10%. These guidelines could subject up to 63% of cases to unnecessary evaluation by Child Protective Services. The purpose of this study was to identify how patient age and femur fracture morphology impact the likelihood that providers assess a fracture as non-accidental and pursue further investigation of possible child abuse. 

Methods:
This study evaluated a questionnaire completed by 75 clinicians from multiple specialties. There were 5 subgroup populations (6, 12, 18, 24, 35 months old) combined with diaphyseal and metaphyseal femur fracture types. For each age group, the same radiograph was presented and described as an oblique diaphyseal fracture in one scenario and spiral diaphyseal fracture in another. Similarly, some cases were described as a corner fracture in one scenario and classic metaphyseal lesion in another. This design assessed if fracture nomenclature, in addition to patient age, impacted clinician suspicion of abuse. Participants assessed case presentations and reported their perceived likelihood the case represented non-accidental trauma utilizing a Likert scale from 1 to 5 corresponding to a percent likelihood. They also reported the percent likelihood they would pursue further investigation. 

Results:
75 questionnaires were analyzed. Mean likelihood of abuse rating in all fracture types for patients 18-35 months was 3.8, corresponding to 61-80% perceived likelihood of abuse. Mean likelihood for further investigation of child abuse in patients 18-35 months of age was 3.7, corresponding to 61-80% clinician likelihood to further investigate. Fracture nomenclature did not significantly impact clinician ratings. In the linear mixed model, the strongest predictors of perceived high likelihood of abuse were respondent specialty, with emergency medicine (p<0.001) and advanced practice providers (p=0.006) having the highest likelihood ratings. 

Conclusions: 
Clinicians are trained to have a high index of suspicion for child abuse in pediatric patients. However, this study demonstrates a high assessment of chance for abuse and low threshold for pursuing further investigation for femoral shaft fractures in walking-age children which contradicts literature that reports actual rates of non-accidental trauma to be lower than 10%. This bias may exhaust hospital and community resources in evaluating toddler femur fractures for abuse and cause unnecessary stress for patients and families.

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Effect of mesenchymal stromal cell delivery through cardiopulmonary bypass in a piglet model