Predictors of social risk for post-ischemic stroke reintegration

After stroke rehabilitation, patients need to reintegrate back into their daily life, workplace and society. Reintegration involves complex processes depending on age, sex, stroke severity, cognitive, physical, as well as socioeconomic factors that impact long-term outcomes post-stroke. Moreover, post-stroke quality of life can be impacted by social risks of inadequate family, social, economic, housing and other supports needed by the patients. Social risks and barriers to successful reintegration are poorly understood yet critical for informing clinical or social interventions. Therefore, the aim of this work is to predict social risk at rehabilitation discharge using sociodemographic and clinical variables at rehabilitation admission and identify factors that contribute to this risk. A Gradient Boosting modelling methodology based on decision trees was applied to a Catalan 217-patient cohort of mostly young (mean age 52.7), male (66.4%), ischemic stroke survivors. The modelling task was to predict an individual's social risk upon discharge from rehabilitation based on 16 different demographic, diagnostic and social risk variables (family support, social support, economic status, cohabitation and home accessibility at admission). To correct for imbalance in patient sample numbers with high and low-risk levels (prediction target), five different datasets were prepared by varying the data subsampling methodology. For each of the five datasets a prediction model was trained and the analysis involves a comparison across these models. The training and validation results indicated that the models corrected for prediction target imbalance have similarly good performance (AUC 0.831-0.843) and validation (AUC 0.881 - 0.909). Furthermore, predictor variable importance ranked social support and economic status as the most important variables with the greatest contribution to social risk prediction, however, sex and age had a lesser, but still important, contribution. Due to the complex and multifactorial nature of social risk, factors in combination, including social support and economic status, drive social risk for individuals.

Understanding and Predicting Cognitive Improvement of Young Adults in Ischemic Stroke Rehabilitation Therapy

Accurate early predictions of a patient's likely cognitive improvement as a result of a stroke rehabilitation programme can assist clinicians in assembling more effective therapeutic programs. In addition, sufficient levels of explainability, which can justify these predictions, are a crucial requirement, as reported by clinicians. This article presents a machine learning (ML) prediction model targeting cognitive improvement after therapy for stroke surviving patients. The prediction model relies on electronic health records from 201 ischemic stroke surviving patients containing demographic information, cognitive assessments at admission from 24 different standardized neuropsychology tests (e.g., TMT, WAIS-III, Stroop, RAVLT, etc.), and therapy information collected during rehabilitation (72,002 entries collected between March 2007 and September 2019). The study population covered young-adult patients with a mean age of 49.51 years and only 4.47% above 65 years of age at the stroke event (no age filter applied). Twenty different classification algorithms (from Python's Scikit-learn library) are trained and evaluated, varying their hyper-parameters and the number of features received as input. Best-performing models reported Recall scores around 0.7 and F1 scores of 0.6, showing the model's ability to identify patients with poor cognitive improvement. The study includes a detailed feature importance report that helps interpret the model's inner decision workings and exposes the most influential factors in the cognitive improvement prediction. The study showed that certain therapy variables (e.g., the proportion of memory and orientation executed tasks) had an important influence on the final prediction of the cognitive improvement of patients at individual and population levels. This type of evidence can serve clinicians in adjusting the therapeutic settings (e.g., type and load of therapy activities) and selecting the one that maximizes cognitive improvement.

Visualization of the Anterior Temporal Artery as a Predictor of Outcome in Middle Cerebral Artery Occlusion Patients Achieving Successful Recanalization After Transfer

Introduction

Anterior temporal artery (ATA) visualization on computed tomography angiography (CTA) has been previously associated with good outcomes in middle cerebral artery (MCA) occlusions, but not in the setting of patients who initially present to non-thrombectomy centers.

Methods

We retrospectively identified acute MCA (M1) occlusion patients who underwent mechanical thrombectomy after transfer from non-thrombectomy-capable centers. Neuroradiologists confirmed the MCA (M1) as the most proximal site of occlusion on CTA and assessed for visualization of the ATA. Thrombolysis in Cerebral Infarction (TICI) 2b or greater revascularization scores were confirmed by neurointerventionalists blinded to patient outcomes. Ninety-day modified Rankin scale (mRS) scores were obtained via a structured telephone questionnaire.

Results

We identified 102 M1 occlusion patients over a three-and-a-half-year period presenting to a non-thrombectomy-capable center who underwent transfer and mechanical thrombectomy. There were no significant differences in age, gender, race, comorbidities, or median National Institute of Health Stroke Scale (NIHSS) scores between the ATA visualized (n = 47) versus non-visualized (n = 55) cohort, and no significant differences in baseline Alberta Stroke Program Early Computed Tomography (ASPECT) scores, post-intervention TICI scores, or interval from last known well to revascularization. There was a strong trend in functional independent outcome (mRS ≤ 2) for patients with ATA visualization (63.8% vs. 45.5%, p = 0.064).

Conclusion

For patients presenting to non-thrombectomy centers without CT perfusion capability, ATA visualization should be further investigated as an outcome predictor, given its association with functional independence after successful recanalization.

This article was previously presented as a meeting abstract at the 2021 International Stroke Conference on March 17-19, 2021.

Recommendations for designing hybrid conferences

During the COVID-19 pandemic, many smaller conferences have moved entirely online and larger ones are being held as hybrid events. Even beyond the pandemic, hybrid events reduce the carbon footprint of conference travel and makes events more accessible to parts of the research community that have difficulty traveling long distances, while preserving most advantages of in-person gatherings.

While we have developed a solid understanding of how to design virtual events over the last two years, we are still learning how to properly run hybrid events. We present guidelines and considerations-spanning technology, organization and social factors-for organizing successful hybrid conferences.

This paper summarizes and extends the discussions held at the Dagstuhl seminar on "Climate Friendly Internet Research" held in July 2021.

Listening Effort Informed Quality of Experience Evaluation

Perceived quality of experience for speech listening is influenced by cognitive processing and can affect a listener's comprehension, engagement and responsiveness. Quality of Experience (QoE) is a paradigm used within the media technology community to assess media quality by linking quantifiable media parameters to perceived quality. The established QoE framework provides a general definition of QoE, categories of possible quality influencing factors, and an identified QoE formation pathway. These assist researchers to implement experiments and to evaluate perceived quality for any applications. The QoE formation pathways in the current framework do not attempt to capture cognitive effort effects and the standard experimental assessments of QoE minimize the influence from cognitive processes. The impact of cognitive processes and how they can be captured within the QoE framework have not been systematically studied by the QoE research community. This article reviews research from the fields of audiology and cognitive science regarding how cognitive processes influence the quality of listening experience. The cognitive listening mechanism theories are compared with the QoE formation mechanism in terms of the quality contributing factors, experience formation pathways, and measures for experience. The review prompts a proposal to integrate mechanisms from audiology and cognitive science into the existing QoE framework in order to properly account for cognitive load in speech listening. The article concludes with a discussion regarding how an extended framework could facilitate measurement of QoE in broader and more realistic application scenarios where cognitive effort is a material consideration.

Speech quality estimation with deep lattice networks

Intrusive subjective speech quality estimation of mean opinion score (MOS) often involves mapping a raw similarity score extracted from differences between the clean and degraded utterance onto MOS with a fitted mapping function. More recent models such as support vector regression (SVR) or deep neural networks use multidimensional input, which allows for a more accurate prediction than one-dimensional (1-D) mappings but does not provide the monotonic property that is expected between similarity and quality. We investigate a multidimensional mapping function using deep lattice networks (DLNs) to provide monotonic constraints with input features provided by ViSQOL. The DLN improved the speech mapping to 0.24 mean-square error on a mixture of datasets that include voice over IP and codec degradations, outperforming the 1-D fitted functions and SVR as well as PESQ and POLQA. Additionally, we show that the DLN can be used to learn a quantile function that is well-calibrated and a useful measure of uncertainty. The quantile function provides an improved mapping of data driven similarity representations to human interpretable scales, such as quantile intervals for predictions instead of point estimates.

Abstract P361: Visualization of the Anterior Temporal Artery as a Predictor of Outcome in Middle Cerebral Artery Occlusion Patients Achieving Successful Recanalization After Interfacility Transfer

Introduction: Many non-thrombectomy centers lack Computerized Tomography Perfusion (CTP) capability. Anterior temporal artery (ATA) visualization on Computerized Tomography Angiography (CTA) has been previously associated with good outcomes in middle cerebral artery (MCA) occlusions, but not in the context of recanalization after interfacility transfer for thrombectomy. We hypothesized that independent functional outcome at 90 days would be greater for MCA occlusion patients initially presenting to non-thrombectomy centers with a visualized ATA on CTA who achieved TICI 2b or greater recanalization after transfer.

Methods: We conducted a retrospective cohort study of patients transferred for mechanical thrombectomy. A neuroradiologist blinded to patient outcomes confirmed the MCA as the most proximal site of occlusion on CTA, and assessed for visualization of the ATA. TICI 2b or greater revascularization scores were confirmed by neurointerventionalists blinded to patient outcomes. Ninety-day mRS scores were obtained via telephone utilizing a structured questionnaire.

Results: We identified a total of 107 MCA occlusion patients over a 3 ½ year period meeting our inclusion criteria. There were no significant differences in age, gender, race, comorbidities, median NIHSS, or time-to-revascularization variables between the ATA visualized (n=50) versus non-visualized (n=57) group, with the exception of significantly more wake-up strokes in the ATA visualized group (34.7% vs 16.1%, p=0.03). There was a non-significant trend for independent outcome (mRS ≤2) at 90 days for patients with ATA visualization compared to those for whom the ATA was not visualized on the CTA (63.8% vs 45.5%, p=0.06).

Conclusion: For MCA occlusion patients initially presenting to non-thrombectomy centers achieving successful recanalization via mechanical thrombectomy, there is a strong trend for visualization of the anterior temporal artery on the CTA performed at the non-thrombectomy center as being a predictor of independent functional outcome. Especially for institutions without CTP capability, this association with ATA visualization should be further investigated as a predictor for good outcome after transfer for successful mechanical thrombectomy.

Abstract P557: Hypoperfusion Intensity Ratio and Cerebral Blood Volume Index as Predictors of Outcome for Recanalized Middle Cerebral Artery Occlusions

Introduction: Preliminary data suggest the Hypoperfusion Intensity Ratio (HIR) and the Cerebral Blood Volume Index (CBVI) derived from Computerized Tomography Perfusion (CTP) imaging predict the rate of collateral flow, speed of infarct growth, and clinical outcome. We hypothesized that functional outcomes at hospital discharge would be significantly better for middle cerebral artery (MCA) occlusion patients achieving Thrombolysis in Cerebral Infarction (TICI) 2b or greater recanalization with presenting hospital CTPs consistent with “good” (HIR <0.5 and CBVI >0.7) versus “poor” (HIR ≥0.5 and CBVI ≤0.7) indices.

Methods: We conducted a retrospective cohort study. A neuroradiologist confirmed the MCA occlusion based on the initial Computerized Tomography Angiogram (CTA). All TICI scores were confirmed by neurointerventionalists blinded to patient outcomes. We defined independent outcome as mRS ≤2, and favorable outcome as an mRS ≤3. We additionally stratified patients as initially presenting to thrombectomy versus non-thrombectomy centers.

Results: We identified a total of 162 patients over a 3 ½ year period with an MCA occlusion achieving TICI 2b recanalization or greater, of whom 67 had good indices and 48 had poor indices. For patients with good compared to poor indices, there was a trend for achieving independent outcome (55% vs 37%, p=0.061) that reached significance for favorable outcome (69% vs 50%, p=0.043). Limiting the analysis to only patients presenting to non-thrombectomy centers (n=67), these findings were consistent, with a trend for achieving independent outcome for good versus poor collaterals (48% vs 30% p=0.173), which was again significant for a favorable outcome (66% vs 39%, p=0.036). Across all patients, HIR <0.5 (n=86) or CBVI >0.7 (n=95) were not independently associated with independent outcomes, but for patients presenting to non-thrombectomy centers, an HIR <0.5 alone (n=51) was significantly associated with favorable outcome.

Conclusion: For MCA occlusion patients achieving TICI 2b recanalization, the combination of good HIR and CBVI is significantly associated with a favorable functional outcome. For patients presenting to non-thrombectomy centers, HIR alone may be sufficient to predict favorable outcome.

0045 Biobehavioral Markers for Sleep/Wake Disturbance and Fatigue in Young Childhood Brain Tumor Survivors

Introduction

Survivors of childhood and adolescent brain tumors and subsequent treatment may experience many neurological processes involving the forebrain, brainstem, and hypothalamus as well as the symptom cluster of stress, sleep, and fatigue. As a result, the impact of brain tumor treatment (chemotherapy/biotherapy, radiotherapy, and surgery) may have lasting biobehavioral effects. Description of symptoms during early survivorship is not always evident in the literature.

Methods

Convenience sampling and the following inclusion criteria were utilized: brain tumor survivors ages 8–17 years; ≥6 months, &lt;6 years from completion of treatment; disease free or stable disease. Participants completed polysomnography (PSG) followed by a multiple sleep latency test (MSLT), and subjective measures of sleep, fatigue, stress, and pubertal status. Collection of salivary biomarkers for stress (cortisol) and sleep (melatonin) was completed the evening of and morning after the PSG.

Results

Analysis of the first 12 participants (5 males; 3 Hispanic/Latino; average age 14 years; 9–72 months post treatment) revealed mean (minutes) total sleep time (TST) 442, sleep latency (SL) 42 and waking (WASO) 88; sleep efficiency (SE) mean 83%, There were large magnitude correlations between several variables of interest, notably PM Cortisol with fatigue, TST (r= .472; -.453); AM Cortisol with SL (r=.479); AM Melatonin with SE, SL, WASO (r= -.459; .692; .458). Average AM melatonin level (26.6 pg/dl) was higher than PM (6.66 pg/dl). Seven participants were diagnosed with clinical sleep disorders, including one with narcolepsy and two with hypersomnia.

Conclusion

During early survivorship after pediatric brain tumor treatment, survivors may be at high risk for sleep/wake disturbance (SWD). Morning melatonin and biomarker correlations with sleep and fatigue in this sample warrant further exploration and may be related to first night effect versus circadian rhythm differences or clinical sleep disorder. Recommendations for future practice include developmentally matched protocols and routine screening of biobehavioral markers to assess risk for stress, SWD, and fatigue.

Support

1. Center for Oncology Education and Research Harris College of Nursing & Health Sciences Texas Christian University 2. Neuro-Oncology Program Hematology/Oncology Center Cook Children’s Health Care System 3. Nursing Research and Evidence-Based Practice James A. “Buddy” Davidson Endowed Fund

A magic-themed upper limb intervention for children with unilateral cerebral palsy: The perspectives of parents

AIM

To explore parent's perspective of their child's participation in a magic-themed intervention called Amazing Magic Club (AMC), and to further our understanding of motivated engagement and the impact of themed group-based interventions for children with unilateral cerebral palsy (CP).

METHODS

Twenty-nine parents of children with unilateral CP completed semi-structured interviews. The child participants (n = 28) attended one of three AMCs; average age of the children was 10y 6mo (SD 2y 2mo). The parent interviews were analysed using thematic analysis.

RESULTS

The three themes are: "It's okay to be me", the magic effect and "I can do it". Parents observed their children to belong and learn about their abilities. The importance of the magicians and the performance is described. Parents observed their children to have increased self-belief and a new willingness to attempt difficult tasks.

DISCUSSION

AMC appears to capture intrinsic motivation for children with unilateral CP to complete challenging tasks.

Upper Limb Function of Children with Unilateral Cerebral Palsy After a Magic-Themed HABIT: A Pre-Post-Study with 3- and 6-Month Follow-Up

Aims: To examine changes in upper limb function, and performance in everyday tasks, for children with unilateral cerebral palsy who participated in a magic-themed hand-arm bimanual intensive therapy (HABIT). Methods: Twenty-eight children participated; mean age 10 y 6 mo (SD 2 y 2 mo), n = 15 male and n = 13 female. Using a single group, pre-and post-test design, the magic-themed HABIT was delivered for 60 hours over 10 days. Bimanual and unimanual hand function were measured using the Assisting Hand Assessment (AHA) and Box and Blocks Test (BBT). Occupational performance was rated using the Canadian Occupational Performance Measure (COPM). Two parent questionnaires explored change in bimanual hand use in everyday activities; ABILHAND-Kids and Children's Hand-use Experience Questionnaire (CHEQ). Assessments were completed pre-, immediately post, 3 months and 6 months after the intervention. Results: Friedman's ANOVA revealed a significant improvement for COPM and CHEQ grasp subscale. Repeated measures ANOVA revealed a significant improvement in BBT, and ABILHAND-Kids, and no significant change for AHA. Conclusions: Children who participated in the magic-themed HABIT experienced improved occupational performance, unimanual skills, and parent ratings of performance in challenging everyday tasks.

ViSQOLAudio: An objective audio quality metric for low bitrate codecs

Streaming services seek to optimise their use of bandwidth across audio and visual channels to maximise the quality of experience for users. This letter evaluates whether objective quality metrics can predict the audio quality for music encoded at low bitrates by comparing objective predictions with results from listener tests. Three objective metrics were benchmarked: PEAQ, POLQA, and VISQOLAudio. The results demonstrate objective metrics designed for speech quality assessment have a strong potential for quality assessment of low bitrate audio codecs.

Simulated performance intensity functions

Measuring speech intelligibility for different hearing aid fitting methods in a simulated environment would allow rapid prototyping and early design assessment. A simulated performance intensity function (SPIF) test methodology has been developed to allow experimentation using an auditory nerve model to predict listeners' phoneme recognition. The test discriminates between normal hearing and progressively degrading levels of sensorineural hearing loss. Auditory nerve discharge patterns, presented as neurograms, can be subjectively ranked by visual inspection. Here, subjective inspection is substituted with an automated ranking using a new image similarity metric that can quantify neurogram degradation in a consistent manner. This work reproduces the test results of a real human listener with moderate hearing loss, in unaided and aided scenarios, using a simulation. The simulated results correlate within comparable error margins to the real listener test performance intensity functions.

Use of bioindicators and passive sampling devices to evaluate ambient ozone concentrations in north central Pennsylvania

Ambient concentrations of tropospheric ozone and ozone-induced injury to black cherry (Prunus serotina) and common milkweed (Asclepias syriaca) were determined in north central Pennsylvania from 29 May to 5 September 2000 and from 28 May to 18 September 2001. Ogawa passive ozone samplers were utilized within openings at 15 forested sites of which six were co-located with TECO model 49 continuous ozone monitors. A significant positive correlation was observed between the Ogawa passive samplers and the TECO model 49 continuous ozone monitors for the 2000 (r=0.959) and 2001 (r=0.979) seasons. In addition, a significant positive correlation existed in 2000 and 2001 between ozone concentration and elevation (r=0.720) and (r=0.802), respectively. Classic ozone-induced symptoms were observed on black cherry and common milkweed. In 2000, initial injury was observed in early June, whereas for the 2001 season, initial injury was initially observed in late June. During both seasons, injury was noted at most sites by mid- to late-July. Soil moisture potential was measured for the 2001 season and a significant positive relationship (P<0.001) showed that injury to black cherry was a function of cumulative ozone concentrations and available soil moisture.

Transformation of Rickettsia prowazekii to erythromycin resistance encoded by the Escherichia coli ereB gene

Rickettsia prowazekii, the etiologic agent of epidemic typhus, is an obligate, intracytoplasmic, parasitic bacterium. Recently, the transformation of this bacterium via electroporation has been reported. However, in these studies identification of transformants was dependent upon either selection of an R. prowazekii rpoB chromosomal mutation imparting rifampin resistance or expression of the green fluorescent protein and flow cytometric analysis. In this paper we describe the expression in R. prowazekii of the Escherichia coli ereB gene. This gene codes for an erythromycin esterase that cleaves erythromycin. To the best of our knowledge, this is the first report of the expression of a nonrickettsial, antibiotic-selectable gene in R. prowazekii. The availability of a positive selection for rickettsial transformants is an important step in the characterization of genetic analysis systems in the rickettsiae.

Sexual dysfunction induced by serotonin reuptake antidepressants

Serotonin reuptake inhibitor (SRI) antidepressants have been associated with sexual dysfunction, though there have been few prospective reports specifically examining this problem. The purpose of this study was to determine if three SRIs affected sexual function in patients with an anxiety disorder or major depressive disorder over a 3-month period. Sixty-one patients were evaluated for at least 2 months in a prospective study of the effects of fluoxetine, sertraline, and paroxetine on five aspects of sexual function: libido, erection/lubrication, orgasm quality, orgasm delay, and sexual frequency. Measurements were made at baseline and at each month on visual analog scales. For men and women, orgasm quality was lower and orgasm delay longer at Months 1, 2, and 3 compared with baseline (p < .001). Erection scores were lower over time (p < .02) but this change was less dramatic. Lubrication, libido, and sexual frequency were not appreciably changed over 3 months. Anorgasmia was significantly more common in women than men at Months 1 and 2. Orgasm appears to be a primary sexual function affected by SRIs.

Bupropion treatment of serotonin reuptake antidepressant-associated sexual dysfunction

Serotonin reuptake inhibitor (SRI)-induced sexual dysfunction is common, and a number of pharmacologic adjunctive strategies have been employed to treat this vexing problem. This open label study tested the efficacy of adjunctive bupropion across several measures of sexual function. Patients taking SRIs for various mood or anxiety disorders who reported prospective decline in sexual function after at least 2 months on SRIs were offered treatment with bupropion, 75 mg/day. Eight patients were treated, and sexual function was measured by use of a visual analog scale at 1 month of treatment. Four of eight patients experienced marked improvement in sexual dysfunction following adjunctive bupropion treatment. Bupropion may be a pharmacologic option for treating SRI-associated sexual dysfunction, though controlled clinical trials are needed.

Molecular evidence for a Mediterranean origin of the Macaronesian endemic genus Argyranthemum (Asteraceae)

The internal transcribed spacers (ITS) of nuclear ribosomal DNA were sequenced for 52 species from 32 genera and eight subtribes of Anthemideae. Phylogenetic analyses of ITS data generated trees that are largely incongruent with the recent classification of Anthemideae; most of the subtribes examined are not resolved as monophyletic. However, ITS trees are congruent with morphological, isozyme, phytochemical, and chloroplast DNA (cpDNA) restriction site data in supporting a Mediterranean origin for Argyranthemum, the largest endemic genus of the Atlantic oceanic islands. A combined analysis of ITS sequences and cpDNA restriction sites indicates that Argyranthemum is sister to the other three genera of Chrysantheminae (i.e., Chrysanthemum, Heteranthemis, and Ismelia). Times of divergence of Argyranthemum inferred from the ITS sequences ranged between 0.26 and 2.1 million years ago (mya) and are lower than values previously reported from isozyme and cpDNA data (1.5-3.0 mya). It is likely that rate heterogeneity of the ITS sequences in the Anthemideae accounts for the low divergence-time estimates. Comparison of data for 20 species in Argyranthemum and Chrysantheminae indicates that the cpDNA restriction site approach provided much more phylogenetic information than ITS sequences. Thus, restriction site analyses of the entire chloroplast genome remain a valuable approach for studying recently derived island plants.

The establishment of a population-based Cancer Registry for North Carolina

In 1984 the North Carolina Medical Society's House of Delegates adopted Report S, which called for the North Carolina Legislature to fund a statewide cancer incident reporting system. The Cancer Committee continues to be advisory to the Division of Adult Health. A subcommittee of the Cancer Committee advises the Central Cancer Registry.

The distribution of serum alanine aminotransferase levels in a blood donor population

The authors studied the distribution of alanine aminotransferase (ALT) levels in 10,034 volunteer blood donors. The mean +/- SD ALT value was 21.4 +/- 19.3 IU/liter; 549 (5.5%) of the donors had a ALT value greater that 45 IU; 2.5 per cent had ALT values greater than 60 IU. In general, ALT levels were higher in males than in females, and were age related; peak values occurred in the third decade of life for males and between 50-60 years of age in females. ALT values greater than 45 IU were found significantly more often in males, in donors of both sexes 30-40 years of age, in married donors, in non-Caucasians, and in those whose education level was no higher than high school. Follow-up samples in donors with an initial ALT greater than 45 IU, revealed that 67% continued to have ALT values above 45 IU 2-8 weeks following initial sampling, and 40% had an ALT greater than 45 IU when tested again six months after entry into the study. ALT values greater than 60 IU were associated with a significantly increased prevalence of antibody of hepatitis B surface antigen (anti-HBs) and antibody to hepatitis B core antigen (anti-HBc) occurring together. No statistically significant association was found between transaminase activity and the prevalence of anti-HBs or anti-HBc alone, or with hepatitis A antibody. These findings demonstrate that there are defined sociodemographic and serologic features of donors with elevated ALT values.

Detection and characterization of monoclonal antibodies to platelet membrane proteins

We have devised a solid-phase radioimmunoassay for the detection and characterization of monoclonal antibodies directed against platelet surface antigens. Platelet membrane proteins, solubilized with 0.1% Triton X-100, were covalently coupled to cyanogen bromide (CNBr)-activated filter paper disks that were than used as the support in antibody binding assays. SDS PAGE of solubilized membrane proteins taken immediately before and after incubation with activated disks indicated that representative amounts of each membrane protein were bound to the disks. Either monoclonal or heterologous anti-platelet antibody could be detected on disks that had been prepared using as little as 50 micrograms of membrane protein per 100 disks. For the detection of antibody, disks were incubated with test sera for 2 h, washed, and incubated with 125I-labeled anti-immunoglobulin G, and the amount of bound radioactivity was determined. The sensitivity of the disk assay in detecting monoclonal antibodies was far greater than that of a corresponding radioimmunoassay that used whole platelets as the solid phase. By linking other proteins such as fibrinogen or anti-mouse subclass specific antisera to CNBr-activated disks, the method was adapted for antibody characterization. The sensitivity and ease with which the assay can be performed make this technique most suitable for screening and characterizing monoclonal antibodies.