The effects of alcohol and aldehyde dehydrogenases on disorders of hematopoiesis.

Hematopoiesis involves the orderly production of millions of blood cells per second from a small number of essential bone marrow cells termed hematopoietic stem cells (HSCs). Ethanol suppresses normal hematopoiesis resulting in leukopenia, anemia, and thrombocytopenia and may also predispose to the development of diseases such as myelodysplasia (MDS) and acute leukemia. Currently the exact mechanisms by which ethanol perturbs hematopoiesis are unclear. The aldehyde dehydrogenase (ALDH) gene family plays a major role in the metabolism of reactive aldehydes derived from ethanol in the liver and other organs. At least one of the ALDH isoforms, ALDH1A1, is expressed at high levels in HSCs in humans, mice, and other organisms. Recent data indicate that ALDH1A1 and possibly other ALDH isoforms may metabolize reactive aldehydes in HSCs and other hematopoietic cells as they do in the liver and elsewhere. In addition, loss of these ALDHs leads to perturbation of a variety of cell processes that may predispose HSCs to disorders in growth and leukemic transformation. From these findings, we suggest a hypothesis that the cytopenias and possible increased risk of MDS and acute leukemia in heavy alcohol users is due to polymorphisms in genes responsible for metabolism of alcohol derived reactive aldehydes and repair of their DNA adducts in HSCs and other hematopoietic cells. In the article, we will summarize the biological properties of hematopoietic cells and diseases related to ethanol consumption, discuss molecular characteristics of ethanol metabolism, and describe a model to explain how ethanol derived reactive aldehydes may promote HSC damage.

Regional approach to competency-based patient care provider disaster training: the Center for Health Professional Training and Emergency Response.

OBJECTIVES: This article details the development of the Center for Health Professional Training and Emergency Response (CHPTER), including its innovative, competency-based emergency preparedness training (EPT) curriculum, and the results of a regional preparedness workforce assessment. METHODS: CHPTER was established in 2009 with the goal of enhancing regional health security and patient surge competency by offering patient care providers, including clinicians and volunteers, hands-on lessons that will protect and save lives during a disaster. A 1-day emergency preparedness training (EPT) course that includes a loud, chaotic clinical disaster scenario was developed. A two-part workforce assessment survey to further refine regional EPT needs was administered. RESULTS: The 1-day EPT course enhanced patient care providers' knowledge, comfort level, and skills required to save lives during a disaster. Twenty-one emergency department directors and 400 patient care providers responded to the surveys. The majority of emergency department directors surveyed believe that one in five of their provider workforce would fail to properly perform their expected duties in a disaster. More than half of the patient care providers reported fewer than 2 hours of annual EPT training and 40% of employers required no annual training. The most significant barriers to widespread dissemination of EPT were financial constraints and time availability of providers. CONCLUSIONS: Patient care providers in our region (North and South Carolina) are not prepared for a disaster. The CHPTER 1-day competency-based EPT curricula improved trainee knowledge, comfort level, and disaster care skills. CHPTER may serve as a model for other regions seeking to improve care provider EPT programs.

Lopinavir/ritonavir for treatment of non-hospitalized patients with COVID-19: a randomized clinical trial.

OBJECTIVES: Effective and widely available therapies are still needed for outpatients with COVID-19. We aimed to evaluate the efficacy and safety of lopinavir/ritonavir (LPV/r) for early treatment of non-hospitalized individuals diagnosed with COVID-19. METHODS: This randomized, placebo (Plb)-controlled, double-blind, multi-site decentralized clinical trial enrolled non-hospitalized adults with confirmed SARS-CoV-2 infection and six or fewer days of acute respiratory infection symptoms who were randomized to either twice-daily oral LPV/r (400 mg/100 mg) or Plb for 14 days. Daily surveys on study days 1 through 16 and again on study day 28 evaluated symptoms, daily activities, and hospitalization status. The primary outcome was longitudinal change in an ordinal scale based on a combination of symptoms, activity, and hospitalization status through day 15 and was analyzed by use of a Bayesian longitudinal proportional odds logistic regression model for estimating the probability of a superior recovery for LPV/r over Plb (odds ratio >1). RESULTS: Between June 2020 and December 2021, 448 participants were randomized to receive either LPV/r (n = 216) or Plb (n = 221). The mean symptom duration before randomization was 4.3 days (SD 1.3). There were no differences between treatment groups through the first 15 days for the ordinal primary outcome (odds ratio 0.96; 95% credible interval: 0.66 to 1.41). There were 3.2% (n = 7) of LPV/r and 2.7% (n = 6) of Plb participants hospitalized by day 28. Serious adverse events did not differ between groups. CONCLUSION: LPV/r did not significantly improve symptom resolution or reduce hospitalization in non-hospitalized participants with COVID-19. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04372628.

Properties of CD34+ CML stem/progenitor cells that correlate with different clinical responses to imatinib mesylate.

Imatinib mesylate (IM) induces clinical remissions in chronic-phase chronic myeloid leukemia (CML) patients but IM resistance remains a problem. We recently identified several features of CML CD34(+) stem/progenitor cells expected to confer resistance to BCR-ABL-targeted therapeutics. From a study of 25 initially chronic-phase patients, we now demonstrate that some, but not all, of these parameters correlate with subsequent clinical response to IM therapy. CD34(+) cells from the 14 IM nonresponders demonstrated greater resistance to IM than the 11 IM responders in colony-forming cell assays in vitro (P < .001) and direct sequencing of cloned transcripts from CD34(+) cells further revealed a higher incidence of BCR-ABL kinase domain mutations in the IM nonresponders (10%-40% vs 0%-20% in IM responders, P < .003). In contrast, CD34(+) cells from IM nonresponders and IM responders were not distinguished by differences in BCR-ABL or transporter gene expression. Interestingly, one BCR-ABL mutation (V304D), predicted to destabilize the interaction between p210(BCR-ABL) and IM, was detectable in 14 of 20 patients. T315I mutant CD34(+) cells found before IM treatment in 2 of 20 patients examined were preferentially amplified after IM treatment. Thus, 2 properties of pretreatment CML stem/progenitor cells correlate with subsequent response to IM therapy. Prospective assessment of these properties may allow improved patient management.

A role for E2F activities in determining the fate of Myc-induced lymphomagenesis.

The phenotypic heterogeneity that characterizes human cancers reflects the enormous genetic complexity of the oncogenic process. This complexity can also be seen in mouse models where it is frequently observed that in addition to the initiating genetic alteration, the resulting tumor harbors additional, somatically acquired mutations that affect the tumor phenotype. To investigate the role of genetic interactions in the development of tumors, we have made use of the Emu-myc model of pre-B and B cell lymphoma. Since various studies point to a functional interaction between Myc and the Rb/E2F pathway, we have investigated the role of E2F activities in the process of Myc-induced lymphomagenesis. Whereas the absence of E2F1 and E2F3 function has no impact on Myc-mediated tumor development, the absence of E2F2 substantially accelerates the time of tumor onset. Conversely, tumor development is delayed by the absence of E2F4. The enhanced early onset of tumors seen in the absence of E2F2 coincides with an expansion of immature B lineage cells that are likely to be the target for Myc oncogenesis. In contrast, the absence of E2F4 mutes the response of the lineage to Myc and there is no expansion of immature B lineage cells. We also find that distinct types of tumors emerge from the Emu-myc mice, distinguished by different patterns of gene expression, and that the relative proportions of these tumor types are affected by the absence of either E2F2 or E2F4. From these results, we conclude that there are several populations of tumors that arise from the Emu-myc model, reflecting distinct populations of cells that are susceptible to Myc-mediated oncogenesis and that the proportion of these cell populations is affected by the presence or absence of E2F activities.

Trial of Early Antiviral Therapies during Non-hospitalized Outpatient Window (TREAT NOW) for COVID-19: a summary of the protocol and analysis plan for a decentralized randomized controlled trial.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has a heterogeneous outcome in individuals from remaining asymptomatic to death. In a majority of cases, mild symptoms are present that do not require hospitalization and can be successfully treated in the outpatient setting, though symptoms may persist for a long duration. We hypothesize that drugs suitable for decentralized study in outpatients will have efficacy among infected outpatients METHODS: The TREAT NOW platform is designed to accommodate testing multiple agents with the ability to incorporate new agents in the future. TREAT NOW is an adaptive, blinded, multi-center, placebo-controlled superiority randomized clinical trial which started with two active therapies (hydroxychloroquine and lopinavir/ritonavir) and placebo, with the hydroxychloroquine arm dropped shortly after enrollment began due to external evidence. Each arm has a target enrollment of 300 participants who will be randomly assigned in an equal allocation to receive either an active therapy or placebo twice daily for 14 days with daily electronic surveys collected over days 1 through 16 and on day 29 to evaluate symptoms and a modified COVID-19 ordinal outcome scale. Participants are enrolled remotely by telephone and consented with a digital interface, study drug is overnight mailed to study participants, and data collection occurs electronically without in-person interactions. DISCUSSION: If effective treatments for COVID-19 can be identified for individuals in the outpatient setting before they advance to severe disease, it will prevent progression to more severe disease, reduce the need for hospitalization, and shorten the duration of symptoms. The novel decentralized, "no touch" approach used by the TREAT NOW platform has distinction advantages over traditional in-person trials to reach broader populations and perform study procedures in a pragmatic yet rigorous manner. TRIAL REGISTRATION: ClinicalTrials.gov NCT04372628. Registered on April 30, 2020. First posted on May 4, 2020.

Machine Learning-Based Exploratory Clinical Decision Support for Newly Diagnosed Patients With Acute Myeloid Leukemia Treated With 7 + 3 Type Chemotherapy or Venetoclax/Azacitidine.

PURPOSE: There are currently limited objective criteria to help assist physicians in determining whether an individual patient with acute myeloid leukemia (AML) is likely to do better with induction with either standard 7 + 3 chemotherapy or targeted therapy with venetoclax plus azacitidine. The study goal was to address this need by developing exploratory clinical decision support methods. PATIENTS AND METHODS: Univariable and multivariable analysis as well as comparison of a range of machine learning (ML) predictors were performed using cohorts of 120 newly diagnosed 7 + 3-treated AML patients compared with 101 venetoclax plus azacitidine-treated patients. RESULTS: A variety of features in the two patient cohorts were identified that may potentially correlate with short- and long-term outcomes, toxicities, and other considerations. A subset of these diagnostic features was then used to develop ML-based predictors with relatively high areas under the curve of short- and long-term outcomes, hospital stays, transfusion requirements, and toxicities for individual patients treated with either venetoclax/azacitidine or 7 + 3. CONCLUSION: Potential ML-based approaches to clinical decision support to help guide individual patients with newly diagnosed AML to either 7 + 3 or venetoclax plus azacitidine induction therapy were identified. Larger cohorts with separate test and validation studies are necessary to confirm these initial findings.

Prediction of blunt traumatic injury in high-acuity patients: bedside examination vs computed tomography.

OBJECTIVE: The addition of spiral computed tomography (SCT) to bedside assessment in patients with major trauma may improve detection of significant injury. We hypothesized that in high-acuity trauma patients, emergency physicians' ability to detect significant injuries based solely on bedside assessment would lack the sensitivity needed to exclude serious injuries when compared with SCT. METHODS: This was a prospective single-cohort study of high-acuity trauma patients routinely undergoing whole-body SCT at a level 1 trauma center from January to September 2006. Before SCT, emergency physicians assigned ratings for likelihood of injury to 5 body regions on the basis of bedside assessment. These ratings were compared with final SCT interpretations. RESULTS: We enrolled 400 patients as a convenience sample; 71 were excluded. When a "very low" rating was considered negative and "low," "intermediate," "high," and "very high" were considered positive, emergency physicians were able to detect head, cervical spine, chest, abdominal/pelvic, and thoracic/lumbar spine injuries with sensitivities (95% confidence interval) of 100% (98.6%-100%), 97.4% (94.9%-98.8%), 96.9% (94.2%-98.4%), 97.9% (95.5%-99.1%), and 97.0% (94.3%-98.5%), respectively. For overall diagnostic accuracy, areas under the receiver operating characteristics curve (95% confidence interval) were 0.87 (0.82-0.92), 0.71 (0.62-0.81), 0.81 (0.76-0.86), 0.77(0.71-0.83), 0.74 (0.65-0.84), respectively. CONCLUSIONS: Bedside assessment by emergency physicians before SCT was sensitive in ruling out serious injuries in high-acuity trauma patients with a "very low" rating for injury. However, overall diagnostic accuracy was low, suggesting that SCT should be considered in most high-acuity patients to prevent missing injuries.

Sleep, Behavior, and Adaptive Function in KAT6A Syndrome.

KAT6A syndrome is a Mendelian Disorder of the Epigenetic Machinery characterized by intellectual disability and profound expressive language impairment. This study aimed to further characterize behavior and sleep in this syndrome. 26 participants between the ages of 3 and 35 years with KAT6A syndrome were assessed via parental informant using the Adaptive Behavior Assessment System version 3 (ABAS-3), Achenbach Child or Adult Behavior Checklist (CBCL/ABCL), and a Modified Simonds and Parraga Sleep Questionnaire (MSPSQ). The ABAS reports conceptual, social, and practical domains of adaptive function as well as a general composite score for adaptive function. The CBCL/ABCL is an inventory that measures internalizing, externalizing, and DSM-oriented problem domains. The MSPSQ is a mix of qualitative and quantitative sleep information that includes behavioral and medical sleep problems. Mean values for all domains of the ABAS-3 were in the extremely low range. Additionally, sleep was very dysfunctional in this cohort. Sixty percent of respondents reported feeling there was a sleep problem, 64% take medication for sleep, and 68% have sought treatment or advice for sleep. Only 12% of these participants have sleep apnea suggesting that sleep problems in this disorder are unrelated to sleep-disordered breathing. Interestingly, there were extremely low rates of all types of behaviors reported among participants on the CBCL/ABCL. No significant differences were seen based on genotype grouping in adaptive function, sleep, or behavior. This study further delineates the phenotype of the KAT6A syndrome and emphasizes the need for supports for adaptive functioning as well as detailed attention to the behavioral aspects of sleep in this condition.

Improved purification of hematopoietic stem cells based on their elevated aldehyde dehydrogenase activity.

BACKGROUND AND OBJECTIVES: Primitive human hematopoietic cells contain higher levels of aldehyde dehydrogenase (ALDH) activity than their terminally differentiating progeny but the particular stages when ALDH levels change have not been well defined. The objective of this study was to compare ALDH levels among the earliest stages of hematopoietic cell differentiation and to determine whether these could be exploited to obtain improved purity of human cord blood cells with long-term lympho-myeloid repopulating activity in vivo. DESIGN AND METHODS: ALDEFLUOR-stained human cord blood cells displaying different levels of ALDH activity were first analyzed for co-expression of various surface markers. Subsets of these cells were then isolated by multi-parameter flow cytometry and assessed for short-and long-term repopulating activity in sublethally irradiated immunodeficient mice. RESULTS: Most short-term myeloid repopulating cells (STRC-M) and all long-term lympho-myeloid repopulating cells (LTRC-ML) stained selectively as ALDH+. Limiting dilution analysis of the frequencies of both STRC-M and LTRC-ML showed that they were similarly and most highly enriched in the 10% top ALDH+ cells. Removal of cells expressing CD2, CD3, CD7, CD14, CD16, CD24, CD36, CD38, CD56, CD66b, or glycophorin A from the ALDH+ low-density fraction of human cord blood cells with low light side-scattering properties yielded a population containing LTRC-ML at a frequency of 1/360. INTERPRETATION AND CONCLUSION: Elevated ALDH activity is a broadly inclusive property of primitive human cord blood cells that, in combination with other markers, allows easy isolation of the stem cell fraction at unprecedented purities.

Predictive value of karyotype on outcome of autotransplants for acute myeloid leukemia in second remission.

The impact of karyotype on the outcome of patients who undergo autotransplant for acute myeloid leukemia (AML) in second remission (CR2) has not been explored. We evaluated the outcomes of 40 patients who proceeded to autotransplant for AML in CR2 at 2 centers. The median age at autotransplant was 50 years (18-64 years) and the median duration of first remission was 15 months (0.8-51 months). High-dose therapy was melphalan 140-160 mg/m2 plus etoposide 60 mg/kg with or without total body irradiation (22), a busulfan-based regimen (17), and cyclophosphamide alone (1). Six patients (15%) died of treatment-related causes within the first 100 days. Event-free and overall survival at 3 years were both 38% (95% confidence interval 23-53%). At a median follow-up of 76 months (2?-?170) in surviving patients, 13 (32.5%) are alive and disease free. Graft purging did not significantly influence survival outcome (P=0.94), although platelet engraftment was significantly delayed (P=0.02). The relative risk of an event (relapse or death) for the karyotype risk groups was favorable 1.0; intermediate 4.2 (1.2-14.7); adverse 9.9 (1.5-63.9); unknown 2.3 (0.6-8.8) (P=0.028). We conclude that patients with AML in CR2 who undergo autotransplant can have durable remissions and those with a good risk karyotype are the most likely to obtain long-term disease-free survival.

Identification of compounds that enhance the anti-lymphoma activity of rituximab using flow cytometric high-content screening.

In this report, we describe a new flow cytometry technique termed flow cytometric high-content screening (FC-HCS) which involves semi-automated processing and analysis of multiparameter flow cytometry samples. As a first test of the FC-HCS technique, we used it to screen a 2000-compound library, called the National Cancer Institute (NCI) Diversity Set, to identify agents that would enhance the anti-lymphoma activity of the therapeutic monoclonal antibody rituximab. FC-HCS identified 15 compounds from the Diversity Set that significantly enhanced the ability of rituximab to inhibit cell cycle progression and induce apoptosis in lymphoma cells. The validity of the screening results was confirmed for several compounds using additional assays of cell proliferation, apoptosis and cell growth. The FC-HCS technique was relatively simple and reliable and could process up to 1000 samples/day on a single flow cytometer. The FC-HCS technique may be useful for a variety of applications including drug discovery, immunologic monitoring of patients, functional genomics studies and tissue engineering efforts.

Pulmonary embolism workup in five steps.

A workup for pulmonary embolism (PE) is complex, with multiple clinical decision rules to remember. A proper diagnostic workup can safely rule out PE without the use of computed tomography, which is both expensive and exposes patients to radiation and intravenous contrast. However, once PE has been diagnosed, it is important to risk stratify patients according to severity to both treat and disposition them correctly. PQRsTU is a simple, easy-to-remember mnemonic for the workup of PE that considers five phases: PERC phase (PE rule-out criteria), Quantify gestalt phase (to determine proper use of D-dimer or direct to imaging), Risk stratification phase (once PE has been diagnosed), Treatment phase, and Unit or floor (patient disposition). This structured method for evaluating PE will help clinicians develop a systematic, evidence-based approach to this complex and potentially lethal disease. Video is available at https://vimeo.com/91406117 Password: perls.

Aldehyde dehydrogenases in acute myeloid leukemia.

Acute myeloid leukemia (AML) affects approximately 15,000 persons per year in the United States and is the sixth leading cause of cancer-related deaths. The treatment of AML has advanced little in the past thirty years, in part because of the biologic heterogeneity of the disease and the difficulty in targeting AML cells while sparing normal hematopoietic cells. Advances in preventing and treating AML are likely to occur once the cellular and molecular differences between leukemia and normal hematopoietic cells are better understood. Aldehyde dehydrogenase (ALDH) activity is highly expressed in hematopoietic stem cells (HSCs), while, in contrast, a subset of AMLs are lacking this activity. This difference may be relevant to the development of AML and may also provide a better avenue for treating this disease. In this review, we summarize what is known about the ALDHs in normal HSCs and AML and propose strategies for capitalizing on these differences in the treatment of acute leukemia, and possibly other cancers as well.

Aldehyde dehydrogenases: from eye crystallins to metabolic disease and cancer stem cells.

The aldehyde dehydrogenase (ALDH) superfamily is composed of nicotinamide adenine dinucleotide (phosphate) (NAD(P)(+))-dependent enzymes that catalyze the oxidation of aldehydes to their corresponding carboxylic acids. To date, 24 ALDH gene families have been identified in the eukaryotic genome. In addition to aldehyde metabolizing capacity, ALDHs have additional catalytic (e.g. esterase and reductase) and non-catalytic activities. The latter include functioning as structural elements in the eye (crystallins) and as binding molecules to endobiotics and xenobiotics. Mutations in human ALDH genes and subsequent inborn errors in aldehyde metabolism are the molecular basis of several diseases. Most recently ALDH polymorphisms have been associated with gout and osteoporosis. Aldehyde dehydrogenase enzymes also play important roles in embryogenesis and development, neurotransmission, oxidative stress and cancer. This article serves as a comprehensive review of the current state of knowledge regarding the ALDH superfamily and the contribution of ALDHs to various physiological and pathophysiological processes.

Fludarabine and cytarabine in patients with relapsed acute myeloid leukemia refractory to initial salvage therapy.

The most effective regimen for relapsed acute myeloid leukemia (AML) patients who do not achieve complete remission (CR) after a course of salvage therapy has not been established. We evaluated the efficacy and toxicity of fludarabine and cytarabine in patients with AML in first relapse who did not respond to a course of salvage chemotherapy with mitoxantrone and etoposide. CR was achieved in 39 % of treated patients, and in 47 % of patients with a favorable/intermediate-risk karyotype. The median overall survival was 4.75 months. The median survival for patients achieving CR with fludarabine-cytarabine was significantly higher than for those who did not respond to therapy (9.6 vs. 4.5 months, P = 0.04). Our data suggest that the fludarabine-cytarabine regimen merits further investigation in relapsed AML patients with favorable or intermediate-risk karyotype with persistent leukemia after a course of salvage therapy.

Varying levels of aldehyde dehydrogenase activity in adult murine marrow hematopoietic stem cells are associated with engraftment and cell cycle status.

Aldehyde dehydrogenase (ALDH) activity is a widely used marker for human hematopoietic stem cells (HSCs), yet its relevance and role in murine HSCs remain unclear. We found that murine marrow cells with a high level of ALDH activity as measured by Aldefluor staining (ALDH(br) cells) do not contain known HSCs or progenitors. In contrast, highly enriched murine HSCs defined by the CD48(-)EPCR(+) and other phenotypes contain two subpopulations, one that stains dimly with Aldefluor (ALDH(dim)) and one that stains at intermediate levels (ALDH(int)). The CD48(-)EPCR(+)ALDH(dim) cells are virtually all in G(0) and yield high levels of engraftment via both intravenous and intrabone routes. In contrast the CD48(-)EPCR(+)ALDH(int) cells are virtually all in G(1), have little intravenous engraftment potential, and yet can engraft long-term after intrabone transplantation. These data demonstrate that Aldefluor staining of unfractionated murine marrow does not identify known HSCs or progenitors. However, varying levels of Aldefluor staining when combined with CD48 and EPCR detection can identify novel populations in murine marrow including a highly enriched population of resting HSCs and a previously unknown HSC population in G(1) with an intravenous engraftment defect.

Aldehyde dehydrogenases are regulators of hematopoietic stem cell numbers and B-cell development.

High levels of the aldehyde dehydrogenase isoform ALDH1A1 are expressed in hematopoietic stem cells (HSCs); however, its importance in these cells remains unclear. Consistent with an earlier report, we find that loss of ALDH1A1 does not affect HSCs. Intriguingly, however, we find that ALDH1A1 deficiency is associated with increased expression of the ALDH3A1 isoform, suggesting its potential to compensate for ALDH1A1. Mice deficient in ALDH3A1 have a block in B-cell development as well as abnormalities in cell cycling, intracellular signaling, and gene expression. Early B cells from these mice exhibit excess reactive oxygen species and reduced metabolism of reactive aldehydes. Mice deficient in both ALDH3A1 and ALDH1A1 have reduced numbers of HSCs as well as aberrant cell cycle distribution, increased reactive oxygen species levels, p38 mitogen-activated protein kinase activity and sensitivity to DNA damage. These findings demonstrate that ALDH3A1 can compensate for ALDH1A1 in bone marrow and is important in B-cell development, both ALDH1A1 and 3A1 are important in HSC biology; and these effects may be due, in part, to changes in metabolism of reactive oxygen species and reactive aldehydes.

Data quality assessment of ungated flow cytometry data in high throughput experiments.

BACKGROUND: The recent development of semiautomated techniques for staining and analyzing flow cytometry samples has presented new challenges. Quality control and quality assessment are critical when developing new high throughput technologies and their associated information services. Our experience suggests that significant bottlenecks remain in the development of high throughput flow cytometry methods for data analysis and display. Especially, data quality control and quality assessment are crucial steps in processing and analyzing high throughput flow cytometry data. METHODS: We propose a variety of graphical exploratory data analytic tools for exploring ungated flow cytometry data. We have implemented a number of specialized functions and methods in the Bioconductor package rflowcyt. We demonstrate the use of these approaches by investigating two independent sets of high throughput flow cytometry data. RESULTS: We found that graphical representations can reveal substantial nonbiological differences in samples. Empirical Cumulative Distribution Function and summary scatterplots were especially useful in the rapid identification of problems not identified by manual review. CONCLUSIONS: Graphical exploratory data analytic tools are quick and useful means of assessing data quality. We propose that the described visualizations should be used as quality assessment tools and where possible, be used for quality control.