Improved accuracy and efficiency of primary care fall risk screening of older adults using a machine learning approach

BACKGROUND

While many falls are preventable, they remain a leading cause of injury and death in older adults. Primary care clinics largely rely on screening questionnaires to identify people at risk of falls. Limitations of standard fall risk screening questionnaires include suboptimal accuracy, missing data, and non-standard formats, which hinder early identification of risk and prevention of fall injury. We used machine learning methods to develop and evaluate electronic health record (EHR)-based tools to identify older adults at risk of fall-related injuries in a primary care population and compared this approach to standard fall screening questionnaires.

METHODS

Using patient-level clinical data from an integrated healthcare system consisting of 16-member institutions, we conducted a case-control study to develop and evaluate prediction models for fall-related injuries in older adults. Questionnaire-derived prediction with three questions from a commonly used fall risk screening tool was evaluated. We then developed four temporal machine learning models using routinely available longitudinal EHR data to predict the future risk of fall injury. We also developed a fall injury-prevention clinical decision support (CDS) implementation prototype to link preventative interventions to patient-specific fall injury risk factors.

RESULTS

Questionnaire-based risk screening achieved area under the receiver operating characteristic curve (AUC) up to 0.59 with 23% to 33% similarity for each pair of three fall injury screening questions. EHR-based machine learning risk screening showed significantly improved performance (best AUROC = 0.76), with similar prediction performance between 6-month and one-year prediction models.

CONCLUSIONS

The current method of questionnaire-based fall risk screening of older adults is suboptimal with redundant items, inadequate precision, and no linkage to prevention. A machine learning fall injury prediction method can accurately predict risk with superior sensitivity while freeing up clinical time for initiating personalized fall prevention interventions. The developed algorithm and data science pipeline can impact routine primary care fall prevention practice.

Testing of an Electronic Clinical Quality Measure for Diagnostic Delay of Venous Thromboembolism (DOVE) in Primary Care

Venous Thromboembolism (VTE) is a serious, preventable public health problem that requires timely treatment. Because signs and symptoms are non-specific, patients often present to primary care providers with VTE symptoms prior to diagnosis. Today there are no federal measurement tools in place to track delayed diagnosis of VTE. We developed and tested an electronic clinical quality measure (eCQM) to quantify Diagnostic Delay of Venous Thromboembolism (DOVE); the rate of avoidable delayed VTE events occurring in patients with a VTE who had reported VTE symptoms in primary care within 30 days of diagnosis. DOVE uses routinely collected EHR data without contributing to documentation burden. DOVE was tested in two geographically distant healthcare systems. Overall DOVE rates were 72.60% (site 1) and 77.14% (site 2). This novel, data-driven eCQM could inform healthcare providers and facilities about opportunities to improve care, strengthen incentives for quality improvement, and ultimately improve patient safety.

Cost Savings Associated With Implementing 4 Total Joint Replacement Electronic Clinical Quality Measures Nationally: 2020-2040

BACKGROUND

Digital transformation using widely available electronic data is a key component to improving health outcomes and customer choice and decreasing cost and measurement burden. Despite these benefits, existing information on the potential cost savings from electronic clinical quality measures (eCQMs) is limited.

METHODS

We assessed the costs of implementing 4 eCQMs related to total hip and/or total knee arthroplasty into electronic health record systems across healthcare systems in the United States. We used published literature and technical expert panel consultation to calculate low-, mid-, and high-range hip and knee arthroplasty surgery projections, and used empirical testing, literature, and technical expert panel consultation to develop an economic model to assess projected cost savings of eCQMs when implemented nationally.

RESULTS

Low-, mid-, and high-range projected cost savings for year's 2020, 2030, and 2040 were calculated for 4 orthopedic eCQMs. Mid-range projected cost savings for 2020 ranged from $7.9 to $31.9 million per measure per year. A breakeven of between 0.5% and 5.1% of adverse events (measure dependent) must be averted for cost savings to outweigh implementation costs.

CONCLUSIONS

All measures demonstrated potential cost savings. These findings suggest that eCQMs have the potential to lower healthcare costs and improve patient outcomes without adding to physician documentation burden. The Centers for Medicare and Medicaid Services' investment in eCQMs is an opportunity to reduce adverse outcomes and excess costs in orthopedics.

Testing a Novel Inpatient Respiratory Depression Electronic Clinical Quality Measure (eCQM) for Orthopedic Practice in Two Large U.S. Health Systems

The objective of this study was to assess the feasibility of using an electronic clinical quality measure (eCQM) to assess inpatient respiratory depression rates following elective primary total hip or total knee arthroplasty using data routinely collected in electronic health records. Measure testing was conducted at two large urban, academic health systems - Mass General Brigham and a geographically distant system in southern U.S. The risk-adjusted inpatient respiratory depression rates were 3.83 and 2.73% for the two health systems, respectively. Clinician group rates ranged from 1.40 to 4.35%, demonstrating opportunity for improvement. Both the data and measure specifications showed strong reliability and validity to allow for calculation of accurate and comparable rates of inpatient respiratory depression.

Testing of a Risk-Standardized Major Bleeding and Venous Thromboembolism Electronic Clinical Quality Measure for Elective Total Hip and/or Knee Arthroplasties

Brigham and Women's Hospital has received funding from the Centers for Medicare and Medicaid Services to develop a novel electronic clinical quality measure to assess the risk-standardized major bleeding and venous thromboembolism (VTE) rate following elective total hip and/or knee arthroplasty. There are currently no existing measures that evaluate both the bleeding and VTE events following joint arthroplasty (TJA). Our novel composite measure was tested within two academic health systems with 17 clinician groups meeting the inclusion criteria. Following risk adjustment, the overall adjusted bleeding rate was 3.87% and ranged between 1.99% - 5.66%. The unadjusted VTE rate was 0.39% and ranged between 0% - 2.65%. The overall VTE/Bleeding composite score was 2.15 and ranged between 1.15 - 3.19. This measure seeks to provide clinician groups with a tool to assess their patient bleeding and VTE rates and compare them to their peers, ultimately providing an evidence-based quality metric assessing orthopedic practices.

Testing of a Risk-Standardized Complication Rate Electronic Clinical Quality Measure (eCQM) for Total Hip and/or Total Knee Arthroplasty

Supported by the Centers for Medicare & Medicaid Services (CMS), Brigham and Women's Hospital (BWH) has retooled the existing claims-based measures NQF1550 and NQF3493 into an electronic clinical quality measure (eCQM) to assess the risk-standardized complication rate (RSCR) following elective primary total hip (THA) and knee arthroplasty (TKA) at the clinician group level. This novel eCQM includes risk-adjustment for social determinants of health, includes all adult patients from all payers, leverages electronic health records (EHRs) rather than claims-based data, and includes both inpatient and outpatient procedures and complications which offers benefits compared to existing metrics. Following testing in two geographically different healthcare systems, the overall risk-standardized complication rate within 90 days following THA and TKA at the two sites was 3.60% (Site 1) and 3.70% (Site 2). This measure is designed for use in the Merit-Based Incentive Payment System (MIPS).

Development of four electronic clinical quality measures (eCQMs) for use in the Merit-based Incentive Payment System (MIPS) following elective primary total hip and knee arthroplasty

The Centers for Medicare & Medicaid Services (CMS) supported Brigham and Women's Hospital (BWH) Center for Patient Safety, Research, and Practice to retool one existing National Quality Forum (NQF) endorsed clinical quality measure (CQM) measure into an electronic clinical quality measure (eCQM) and develop three new eCQMs related to orthopedic care. This manuscript details the iterative process of measure development through environmental scans and stakeholder feedback prior to testing at two geographically different sites. The four measures under development are the: Risk Standardized Complication Rate (RSCR), Risk Standardized Venous Thromboembolism and Major Bleeding Rate (VTE/Bleeding), Risk Standardized Prolonged Opioid Prescribing Rate (POP), and the Risk Standardized Inpatient Respiratory Depression Rate (IRD).

Multi-Site Testing of an Opioid Prescribing Electronic Clinical Quality Measure Following Elective Primary Total Hip and/or Total Knee Arthroplasties

As the United States faces the third wave of the ongoing opioid epidemic, development of measures which report on prolonged opioid prescribing (POP) rates, specifically following orthopedic surgeries, are needed to better understand and improve prescribing practices at the clinician group level. Brigham and Women's Hospital (BWH) has been contracted by the Centers for Medicare and Medicaid Services (CMS) to create a novel electronic clinical quality measure (eCQM) to quantify the prolonged opioid prescribing rate of opioid episodes lasting > 42 days in patients aged 18+ years following elective primary total hip arthroplasties (THA) and/or total knee arthroplasties (TKA) for use in the Merit-Based Incentive Payment System (MIPS). When this measure was tested on two geographically distinct sites, it was found that the THA rate was 3.80% and 16.07% at sites 1 and 2, respectively, and that the TKA rate is 7.65% and 24.15% at sites 1 and 2, respectively. This manuscript reports on the testing of this eCQM between these two sites, highlighting differences in state and organizational level policies regarding opioid prescribing and documentation practices.

The Communicating Narrative Concerns Entered by Registered Nurses (CONCERN) Clinical Decision Support Early Warning System: Protocol for a Cluster Randomized Pragmatic Clinical Trial

Background

Every year, hundreds of thousands of inpatients die from cardiac arrest and sepsis, which could be avoided if those patients’ risk for deterioration were detected and timely interventions were initiated. Thus, a system is needed to convert real-time, raw patient data into consumable information that clinicians can utilize to identify patients at risk of deterioration and thus prevent mortality and improve patient health outcomes. The overarching goal of the COmmunicating Narrative Concerns Entered by Registered Nurses (CONCERN) study is to implement and evaluate an early warning score system that provides clinical decision support (CDS) in electronic health record systems. With a combination of machine learning and natural language processing, the CONCERN CDS utilizes nursing documentation patterns as indicators of nurses’ increased surveillance to predict when patients are at the risk of clinical deterioration.

Objective

The objective of this cluster randomized pragmatic clinical trial is to evaluate the effectiveness and usability of the CONCERN CDS system at 2 different study sites. The specific aim is to decrease hospitalized patients’ negative health outcomes (in-hospital mortality, length of stay, cardiac arrest, unanticipated intensive care unit transfers, and 30-day hospital readmission rates).

Methods

A multiple time-series intervention consisting of 3 phases will be performed through a 1-year period during the cluster randomized pragmatic clinical trial. Phase 1 evaluates the adoption of our algorithm through pilot and trial testing, phase 2 activates optimized versions of the CONCERN CDS based on experience from phase 1, and phase 3 will be a silent release mode where no CDS is viewable to the end user. The intervention deals with a series of processes from system release to evaluation. The system release includes CONCERN CDS implementation and user training. Then, a mixed methods approach will be used with end users to assess the system and clinician perspectives.

Results

Data collection and analysis are expected to conclude by August 2022. Based on our previous work on CONCERN, we expect the system to have a positive impact on the mortality rate and length of stay.

Conclusions

The CONCERN CDS will increase team-based situational awareness and shared understanding of patients predicted to be at risk for clinical deterioration in need of intervention to prevent mortality and associated harm.

Trial Registration

ClinicalTrials.gov NCT03911687; https://clinicaltrials.gov/ct2/show/NCT03911687

International Registered Report Identifier (IRRID)

DERR1-10.2196/30238

Development and Alpha Testing of Specifications for a Prolonged Opioid Prescribing Electronic Clinical Quality Measure (eCQM)

Brigham and Women's Hospital (BWH) has received funding from the Centers for Medicare and Medicaid Services (CMS) to design and implement an electronic clinical quality measure (eCQM) assessing the rate of prolonged opioid prescribing practices following Total Hip Arthroplasty (THA) and Total Knee Arthroplasty (TKA). Utilizing an existing guideline, 'prolonged prescribing' has been defined as opioid prescriptions that exceed 42 days (6 weeks) following surgery. This measure was tested on 12,803 Partners' Healthcare (PHS) patients. Findings demonstrated that after 42 days, meeting the criteria for 'prolonged prescribing' as defined by the proposed measure, 3.7% of THA patients and 12.1% of TKA patients were still receiving opioids. With a better understanding of how specific clinician group post-operative prescribing practices compare with their peers and incorporating monetary incentives through the MIPS participation pathway of the Quality Payment Program (QPP), this measure will motivate orthopedic practices to improve their prescribing patterns, ultimately driving evidence-based quality improvement.

Re-tooling an Existing Clinical Quality Measure for Chronic Opioid Use to an Electronic Clinical Quality Measure (eCQM) for Post-Operative Opioid Prescribing: Development and Testing of Draft Specifications

The objective was to re-tool the existing claims-based measure NQF2940 "Use of Opioids at High Dosage in Persons Without Cancer" to an electronic clinical quality measure (eCQM) for use by orthopedic practices to assess potentially inappropriate high-dose post-operative opioid prescribing practices. Measure specifications were revised based on stakeholder feedback, initial testing and a targeted review of the literature. The eCQM was developed and alpha tested on 9,108 opioid-naive patients who received an elective primary total hip or total knee arthroplasty at Mass General Brigham formerly Partners HealthCare System) from 2016 to 2018. Thirty-eight percent of patients were prescribed high doses (defined as an average daily dose ≥90 morphine milligram equivalents) for the duration of their post-operative opioid prescriptions, demonstrating that this is a meaningful performance measure with substantial opportunity for improvement. National implementation and reporting of this eCQM could be used to facilitate quality improvement to deliver standardized, safe and high-quality care.

Imaging biomarkers of adiposity and sarcopenia as potential predictors for overall survival among patients with endometrial cancer treated with bevacizumab

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Elevated visceral fat area may be a negative prognostic marker in women undergoing treatment for endometrial cancer.

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Treatment with bevacizumab in this cohort of women did not impact overall or progressive free survival.

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When evaluated based on treatment with or without bevacizumab, no marker of adiposity was prognostic of outcomes.

Objective

To examine associations of body mass index (BMI), subcutaneous fat area (SFA) and density (SFD), visceral fat area (VFA) and density (VFD) and total psoas area (TPA) to outcomes among patients receiving chemotherapy with or without bevacizumab for advanced or recurrent endometrial cancer (EC).

Methods

This was a multi-institutional, retrospective study of patients with EC treated with and without bevacizumab as part of front-line, platinum based chemotherapy. Demographics and clinical characteristics were collected. SFA, VFA, SFD, VFD, and TPA were determined from pre-treatment CT scans using a deep learning algorithm. Data was compared with overall survival (OS) and progression free survival (PFS).

Results

Seventy-eight patients were analyzed. The majority were Caucasian (87.2%) with a mean BMI of 34.7 kg/m². PFS and OS did not differ between patients with BMI, SFA, VFA, SFD, VFD, or TPA ≥ the 50th percentile compared to <50th percentile (p = 0.91, 0.45, 0.71, 0.74, 0.60, and 0.74 respectively) and (p = 0.99, 0.59, 0.14, 0.77, and 0.85 respectively). When adjusting for prognostic factors, elevated VFA trended towards shorter OS (25.1 vs 59.5 months, HR = 1.68 [0.92–3.05]).

Patients receiving bevacizumab had similar OS compared to those who did not (37.6 vs 44.5 months, p = 0.409). When stratified by adiposity markers, no subset demonstrated benefit from bevacizumab.

Conclusion

Obesity has been associated with increased levels of vascular endothelial growth factor (VEGF), the main target for bevacizumab therapy. Imaging measurements of VFA may provide prognostic information for patients with EC but no adiposity marker was predictive of improved response to bevacizumab.

Measurements of adiposity as prognostic biomarkers for survival with anti-angiogenic treatment in epithelial ovarian cancer: An NRG Oncology/Gynecologic Oncology Group ancillary data analysis of GOG 218

OBJECTIVE

Adiposity has been hypothesized to interfere with the activity of bevacizumab (BEV), an anti-angiogenic agent. Measurements of adiposity, BMI, surface fat area (SFA), and visceral fat area (VFA) were investigated as prognostic of oncologic outcomes among patients treated with chemotherapy, with or without BEV, on GOG 218, a prospective phase III trial.

METHOD

Pretreatment computed tomography (CT) for 1538 GOG 218 participants were analyzed. Proportional hazards models assessed association between adiposity and overall survival (OS) adjusted for other prognostic factors. The predictive value of adiposity as a function of BEV treatment was assessed in 1019 patients randomized to either chemotherapy (CT) + placebo (P) → P or CT + BEV → BEV.

RESULTS

After adjusting for prognostic factors, SFA was not associated with the overall hazard of death (p = 0.981). There was a non-significant 0.1% (p = 0.062) increase in hazard of death associated with a unit increase in VFA. When comparing the treatment HRs for patients who did and did not receive BEV, there was no association with SFA (p = 0.890) or VFA (p = 0.106). A non-significant 0.8% increase in the hazard of death with unit increase in BMI (p = 0.086) was observed. BMI values were not predictive of a longer survival for patients with BEV vs placebo (p = 0.606).

CONCLUSION

Measures of adiposity strongly correlated to one another but were not predictive of efficacy for BEV. VFA is a weak prognostic factor.

Facile gold nanorod purification by fractionated precipitation

An efficient and facile size- and shape-selective separation of gold nanorod (GNR) solutions is developed using a fractionated precipitation strategy. This convenient method has the benefit of eliminating nanoparticulate side products that can substantially deteriorate the quality of self-assembled nanostructures. The fabrication of advanced plasmonic metamaterials crucially depends on the capacity to supply feedstocks of high-purity building blocks.

mKlf7, a potential transcriptional regulator of TrkA nerve growth factor receptor expression in sensory and sympathetic neurons

Development of the nervous system relies on stringent regulation of genes that are crucial to this process. TrkA, the receptor for nerve growth factor (NGF), is tightly regulated during embryonic development and is essential for the survival and differentiation of neural crest-derived sensory and sympathetic neurons. We have previously identified a mouse TrkA enhancer and have characterized several cis regulatory elements that are important for appropriate TrkA expression in vivo. We now report the cloning of a novel gene encoding a Kruppel-like factor from a mouse dorsal root ganglion expression library. This Kruppel-like factor, named mKlf7, binds specifically to an Ikaros core binding element that is crucial for in vivo TrkA enhancer function. Using in situ hybridization, we demonstrate that mKlf7 is coexpressed with TrkA in sensory and sympathetic neurons during embryogenesis and in adulthood. These data are consistent with the idea that mKlf7 may directly regulate TrkA gene expression in the peripheral nervous system.

Characterization of human A(2B) adenosine receptors: radioligand binding, western blotting, and coupling to G(q) in human embryonic kidney 293 cells and HMC-1 mast cells

Recombinant human A(2B) adenosine receptors (A(2B)ARs) and receptors extended on the amino terminus with hexahistidine and the FLAG epitope, DYKDDDDK (H/F-A(2B)) were stably overexpressed (to >20,000 fmol/mg protein) in human embryonic kidney 293 cells (HEK-A(2B)). By Western blotting, the H/F-A(2B) receptor runs as a 34.8-kDa glycoprotein. Pharmacological properties of A(2B)ARs were characterized with (125)I-3-aminobenzyl-8-phenyl-(4-oxyacetic acid)-1-propylxanthine (K(D), 36 nM). In competition binding assays, the affinity of agonists is reduced by substitution on either the N(6)- or the C-2 position of the adenine ring, whereas 5'-substitutions increase affinity, resulting in the potency order: 5'-N-ethylcarboxamidoadenosine (NECA) >> N(6)-aminobenzyl-NECA approximately 2-chloroadenosine > 2-[4-(2-carboxyethyl)phenethylamino]-NECA (CGS21680) > N(6)-aminobenzyladenosine. The A(2B)AR is potently blocked by the A(2A)-selective antagonist 4-(2-[7-amino-2-[2-furyl][1,2, 4]triazolo-[2,3-a][1,3,5] triazin-5-yl-amino]ethyl)phenol (ZM241385; K(I), 32 nM for A(2B), 1.4 nM for A(2A)) and the A(1) selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (K(I), 50.5 nM for A(2B); 2.5 nM for A(1)). The K(I) values for the antiasthmatic xanthines, theophylline (7.8 microM) and enprofylline (6.4 microM), are below their therapeutic plasma concentrations (20 to 50 microM), and agree with K(I) determinations for inhibition of NECA-stimulated cAMP accumulation in HEK-A(2B) cells. NECA or N(6)-(2-iodo)benzyl-5'-N-methylcarboxamidodoadenosine (IB-MECA) stimulate inositol trisphosphates and calcium accumulation in HEK-A(2B) or HEK-A(3) cells, respectively, but only the A(3) response is prevented by pertussis toxin. In human HMC-1 mast cells, A(2B)AR activation stimulates calcium mobilization and cAMP accumulation. We conclude that HEK-A(2B) cells and HMC-1 mast cells possess A(2B)AR glycoproteins that are coupled to both G(q/11) and G(s).

Adenosine A1 receptor agonist GR79236 suppresses apnea during all sleep stages in the rat

We tested the hypothesis that N-[(1S, trans)-2-hydroxycyclopentyl]adenosine (GR79236), a novel adenosine A1 receptor agonist, would suppress sleep-related apnea in the rat at doses not associated with hypotension or hypothermia. Nine adult Sprague-Dawley rats were instrumented for chronic recording of sleep by electroencephalographic and electromyographic monitoring. Respirations were measured by single chamber plethysmograph, and blood pressure and heart period were transduced by a telemetric implant. Each rat was polygraphically recorded for 6 hours on four occasions in random order, with recordings for an individual animal separated by at least 3 days. Fifteen minutes prior to each recording (0945 hours) each animal received a 1 ml/kg intraperitoneal bolus injection of one of four injectates: saline (control) or 0.03 mg/kg, 0.3 mg/kg, or 3 mg/kg of GR79236. The study was a repeated-measures balanced design such that each animal was recorded exactly once for each injectate. The rate of spontaneous apneas (pauses > 2.5 seconds) was significantly reduced during all sleep stages by all doses of GR79236. At the highest dose, apnea index was reduced by over 70% in both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. In contrast, GR79236 had no effect on sleep stage volumes or blood pressure at any dose tested. Heart rate and core temperature were reduced only at the highest dose (3 mg/kg). We conclude that the adenosine A1 receptor agonist GR79236 significantly suppresses apnea expression in all sleep stages at doses not associated with significant changes in sleep architecture, blood pressure, heart rate, or core temperature.

Isolation and characterization of temperature-sensitive and thermostable mutants of the human receptor-like protein tyrosine phosphatase LAR

Human LAR is a transmembrane receptor-like protein whose cytoplasmic region contains two tandemly duplicated domains homologous to protein tyrosine phosphatases (PTPases). Whereas the membrane-proximal domain I has enzymatic activity, the membrane-distal domain II has no apparent catalytic activity but seems to have a regulatory function. In order to study structure-function relationships of the LAR PTPase, LAR domain I was expressed in Escherichia coli, and mutants that have reduced catalytic activity or reduced thermostability were isolated and characterized. We isolated 18 unique hydroxylamine-induced missense mutations in the LAR domain I segment, of which three were temperature-sensitive. Five additional temperature-sensitive mutations were isolated using N-methyl-N'-nitro-N-nitrosoguanidine. All eight temperature-sensitive mutations are confined within a short segment of the LAR domain I sequence between amino acid positions 1329 and 1407. To examine whether this region is particularly prone to temperature-sensitive mutations, tyrosine at amino acid position 1379 was changed to a phenylalanine by oligonucleotide-directed mutagenesis. This mutant, Y1379-F, was indeed temperature-sensitive. We also isolated a revertant of a temperature-sensitive mutant. The revertant contained a second-site mutation (C1446-Y) that suppresses several temperature-sensitive mutations and also enhances the folding of LAR protein produced in E. coli.

Distinct functional roles of the two intracellular phosphatase like domains of the receptor-linked protein tyrosine phosphatases LCA and LAR

Protein tyrosine phosphorylation is regulated by both protein tyrosine kinases and protein tyrosine phosphatases (PTPases). Recently, the structures of a family of PTPases have been described. In order to study the structure-function relationships of receptor-linked PTPases, we analyzed the effects of deletion and point mutations within the cytoplasmic region of the receptor-linked PTPases, LCA and LAR. We show that the first of the two domains has enzyme activity by itself, and that one cysteine residue in the first domain of both LCA and LAR is absolutely required for activity. The second PTPase like domains do not have detectable catalytic activity using a variety of substrates, but sequences within the second domains influence substrate specificity. The functional significance of a stretch of 10 highly conserved amino acid residues surrounding the critical cysteine residue located in the first domain of LAR was assessed. At most positions, any substitution severely reduced enzyme activity, while missense mutations at the other positions tested could be tolerated to varying degrees depending on the amino acid substitution. It is suggested that this stretch of amino acids may be part of the catalytic center of PTPases.

Nucleotide sequence analyses of the genes encoding the HN, M, NP, P, and L proteins of two host range mutants of Sendai virus

Comparative nucleotide sequence analyses of the genome of Sendai virus (strain Z) and two host range mutants, ts-f1 and F1-R, previously described revealed that the ts defect of ts-f1 can be attributed to two nucleotide exchanges in the NP gene. These exchanges lead to a single amino acid substitution. A single base pair change was found in both the P and L genes of F1-R, but not of ts-f1. Both host range mutants have the two same exchanges in the M gene. These additional mutations are discussed concerning their significance in the pantropic properties of the host range mutants.