Biomedical subjects

P W Stratford

Publications and source records attributed to P W Stratford.

At least 19 recordsLinked to original sources

PubMed2006

Measurement properties of the WOMAC LK 3.1 pain scale.

OBJECTIVE: The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is applied extensively to patients with osteoarthritis of the hip or knee. Previous work has challenged the validity of its physical function scale however an extensive evaluation of its pain scale has not been reported. Our purpose was to estimate internal consistency, factorial validity, test-retest reliability, and the standard error of measurement (SEM) of the WOMAC LK 3.1 pain scale. METHOD: Four hundred and seventy-four patients with osteoarthritis of the hip or knee awaiting arthroplasty were administered the WOMAC. Estimates of internal consistency (coefficient alpha), factorial validity (confirmatory factor analysis), and the SEM based on internal consistency (SEM(IC)) were obtained. Test-retest reliability [Type 2,1 intraclass correlation coefficients (ICC)] and a corresponding SEM(TRT) were estimated on a subsample of 36 patients. RESULTS: Our estimates were: internal consistency alpha=0.84; SEM(IC)=1.48; Type 2,1 ICC=0.77; SEM(TRT)=1.69. Confirmatory factor analysis failed to support a single factor structure of the pain scale with uncorrelated error terms. Two comparable models provided excellent fit: (1) a model with correlated error terms between the walking and stairs items, and between night and sit items (chi2=0.18, P=0.98); (2) a two factor model with walking and stairs items loading on one factor, night and sit items loading on a second factor, and the standing item loading on both factors (chi2=0.18, P=0.98). CONCLUSION: Our examination of the factorial structure of the WOMAC pain scale failed to support a single factor and internal consistency analysis yielded a coefficient less than optimal for individual patient use. An alternate strategy to summing the five-item responses when considering individual patient application would be to interpret item responses separately or to sum only those items which display homogeneity.

Aged↗

PubMed2006

Protocol of the COSMIN study: COnsensus-based Standards for the selection of health Measurement INstruments.

BACKGROUND: Choosing an adequate measurement instrument depends on the proposed use of the instrument, the concept to be measured, the measurement properties (e.g. internal consistency, reproducibility, content and construct validity, responsiveness, and interpretability), the requirements, the burden for subjects, and costs of the available instruments. As far as measurement properties are concerned, there are no sufficiently specific standards for the evaluation of measurement properties of instruments to measure health status, and also no explicit criteria for what constitutes good measurement properties. In this paper we describe the protocol for the COSMIN study, the objective of which is to develop a checklist that contains COnsensus-based Standards for the selection of health Measurement INstruments, including explicit criteria for satisfying these standards. We will focus on evaluative health related patient-reported outcomes (HR-PROs), i.e. patient-reported health measurement instruments used in a longitudinal design as an outcome measure, excluding health care related PROs, such as satisfaction with care or adherence. The COSMIN standards will be made available in the form of an easily applicable checklist. METHOD: An international Delphi study will be performed to reach consensus on which and how measurement properties should be assessed, and on criteria for good measurement properties. Two sources of input will be used for the Delphi study: (1) a systematic review of properties, standards and criteria of measurement properties found in systematic reviews of measurement instruments, and (2) an additional literature search of methodological articles presenting a comprehensive checklist of standards and criteria. The Delphi study will consist of four (written) Delphi rounds, with approximately 30 expert panel members with different backgrounds in clinical medicine, biostatistics, psychology, and epidemiology. The final checklist will subsequently be field-tested by assessing the inter-rater reproducibility of the checklist. DISCUSSION: Since the study will mainly be anonymous, problems that are commonly encountered in face-to-face group meetings, such as the dominance of certain persons in the communication process, will be avoided. By performing a Delphi study and involving many experts, the likelihood that the checklist will have sufficient credibility to be accepted and implemented will increase.

Clinical Protocols↗

PubMed2002

Analysis of a phosphorylcholine-based polymer coating on a coronary stent pre- and post-implantation.

There has been a move towards surface treatments for metallic coronary stents in an effort to improve their compatibility within the body and to provide a vehicle for the delivery of therapeutics. The Biodiv Ysio range of stents is characterised by a biocompatible coating comprised of a crosslinked phosphorylcholine (PC)-based polymer. In addition to a review of some of the data collected to support safety and efficacy of this device, this paper also describes a number of techniques that have been employed to both visualise and quantify the coating on the stent. Explantation of both coated and uncoated stents from porcine coronary arteries revealed that both coated and uncoated stents were >90% endothelialised after 5 days. Typical histological analysis of stented vessel sections after 4 and 12 weeks implantation showed the presence of cell types characteristic of the inflammatory response associated with the trauma caused by stent placement, with no evidence for any additional coating-related adverse inflammatory sequelae. Finally, it was demonstrated by AFM and SEM that both the thickness and force required to remove the coating were essentially unchanged after 6 months implantation. Thus, both the long-term stability and relative biological inertness of the coating has been confirmed in vivo, supporting its use as a vehicle for local drug delivery.

Animals↗

PubMed2001

Crosslinkable coatings from phosphorylcholine-based polymers.

2-Methacryloyloxyethyl phosphorylcholine (MPC) was synthesised and then used in the preparation of crosslinked polymer membranes with lauryl methacrylate, hydroxypropyl methacrylate and trimethoxysilylpropyl methacrylate (crosslinker) comonomers. Some physical aspects of the membrane properties were evaluated in order to establish the basis for the synthesis of a series of post-crosslinkable polymers. These materials were made by copolymerisation of the constituent monomers via a free radical method, and characterised using NMR, FT-IR, viscometry and elemental analysis. The optimum crosslink density and conditions required for curing coatings of these polymers were investigated using atomic force microscopy (AFM) and showed the inclusion of 5 mol% silyl crosslinking agent to be ideal. A nanoindentation technique was employed to determine if the coating developed elasticity upon crosslinking. The biological properties of the coatings were evaluated using a variety of protein adsorption assays and blood contacting experiments, and an enzyme immunoassay was developed to detect E. coli in order to assess the level of bacterial adhesion to these biomaterials. Polymers of this type were shown to be very useful as coating materials for improving the biocompatibility of, or reducing the levels of adherent bacteria to medical devices.

Bacterial Adhesion↗

PubMed2001

A novel phosphorylcholine-coated contact lens for extended wear use.

The preparation and characterisation of a new phosphorylcholine (PC)-coated silicone hydrogel contact lens for use in extended wear is described. The Michael-type addition of amines to acrylates forms the basis of the synthesis of a novel silicone-based macromer with hydrophilic functionality. It is demonstrated that this macromer can be combined with other silicone-based monomers, hydrophilic monomers and crosslinker to produce a contact lenses formulation. Examples of lenses with water contents of 33% and 46% are illustrated and their properties compared to other commercially available lenses. Materials with comparatively low modulus (<0.3 MPa) and adequate tear strength (>2-4MPa) with excellent elongation to break (>200%) can be obtained using this technology. In addition to the mechanical aspects. both the oxygen and solute permeabilities of the material can be controlled by the hydrophilic: hydrophobic monomer balance in the formulation. to obtain materials with attributes suitable for extended wear use. The PC coating is achieved by means of an in-mould coating (IMC) technique that produces a uniform and stable surface as determined by staining and XPS. The coating imparts both improved lens wettability (advancing contact angle of approximately 50 with virtually no hysteresis) and lower protein adsorption relative to the uncoated lens.

Adsorption↗

PubMed2001

Use of SF-36 and SF-12 health status measures: a quantitative comparison for groups versus individual patients.

BACKGROUND: The extent to which SF-12 scores reflect SF-36 scores has not been well studied. OBJECTIVES: One purpose was to compare the sensitivity to change of the SF-36 Physical Function sub-score, and the Physical Component Summary Scores (PCS) of the SF-36 and SF-12 on patients with low back pain (LBP). A second purpose was to determine if the SF-12 could serve as a surrogate measure for the SF-36 when making decisions about individual patients. SUBJECTS: The sample consisted of 101 consecutive patients. MEASURES: SF-36 questionnaires were completed by patients at both initial and discharge examinations. SF-12 scores were calculated from the completed SF-36 questionnaires. Therapists' judgments of whether patients were judged to have returned to premorbid function served as the construct for meaningful clinical change. ANALYSIS: Receiver Operating Characteristic (ROC) curve analysis and repeated measures MANCOVA were used to assess sensitivity to change. Linear regression and 95% prediction bands described the extent to which SF-12 scores predict individual SF-36 scores. RESULTS: No significant differences were found between the ROC curve areas for the Physical Function sub-scale, the PCS-36 and PCS-12. No significant differences were found for the comparison of change scores between PF-36, PCS-36 and PCS-12 scores. CONCLUSION: The findings suggest that Physical Function sub-scores, SF-36 and SF-12 PCS scores are equally sensitive to change. SF-12 PCS scores do not adequately predict SF-36 PCS scores for individual patients. The PCS-12 should probably not be used to make judgments about the health status of individual patients with LBP.

Activities of Daily Living↗

PubMed2000

Development and initial validation of the back pain functional scale.

STUDY DESIGN: A prospective repeated-measures design was applied. OBJECTIVES: To examine the measurement properties of the Back Pain Functional Scale (BPFS) and the Roland-Morris Questionnaire (RMQ) and to formulate hypotheses and sample size estimates for a subsequent comparison study. SUMMARY OF BACKGROUND DATA: Although there are numerous functional status measures for patients with low back pain, most have been conceived of and validated with a group rather than an individual patient as the unit of interest. Also, little has been done to formally compare-this includes the generation of a priori hypotheses, followed by statistical hypotheses testing-the many competing measures. METHODS: Subjects were 77 patients with low back pain who were referred by physicians to 10 outpatient physical therapy clinics located in Canada and the United States. The questionnaires were administered at patients' initial visits, within 48 hours of the initial visit, and at 1-, 2-, and 3-week follow-up visits. Reliability, cross-sectional validity, and longitudinal validity (sensitivity to change) coefficients were calculated. RESULTS: Test-retest reliability estimates of 0.81 and 0. 88 were obtained for the RMQ and BPFS, respectively. The measures demonstrated similar levels of cross-sectional validity. Correlations of 0.56 and 0.65 were noted between a prognostic rating of change and the RMQ and BPFS, respectively. The RMQ demonstrated a ceiling effect. Approximately 180 patients are needed for a subsequent head-to-head comparison study of the measures. CONCLUSIONS: The BPFS appears to have sound measurement properties, and a formal head-to-head comparison study with the RMQ is warranted.

Adolescent↗

PubMed2000

Synthesis and characterisation of phosphorylcholine-based polymers useful for coating blood filtration devices.

Copolymers of 2-methacryloyloxyethylphosphorylcholine (MPC) and lauryl methacrylate (LMA) of molar ratios MPC: LMAX where x = 1, 2 or 4, have been synthesised by two different free-radical polymerisation techniques. The solubility characteristics of the resulting materials were investigated in a variety of water: alcohol solvent mixtures and found to be influenced not only by the molar ratio of MPC: LMA, but also the method of synthesis. A window of solubility was observed for certain copolymers and the alcohol used in the solvent mixture was also found to have a profound influence on the solubility profile of the polymers. These materials were soluble in a wider range of aqueous methanol mixtures compared to aqueous mixtures of higher aliphatic alcohols, such as ethanol or isopropyl alcohol, which was rationalised in terms of the affinity of the phosphorylcholine headgroup for the various alcohols relative to water. 1H nuclear magnetic resonance spectroscopy was used to further examine the solution properties of the copolymers in various solvents. The copolymer MPC: LMA2 was coated onto a variety of substrates from both alcohol-only and water: alcohol solvent systems and the surface properties of the films compared by static and dynamic contact angle, atomic force microscopy (AFM) and attenuated internal reflectance Fourier transform infrared spectroscopy (ATR-IR). The coating formed from the water: alcohol solvent was found to be hydrophilic in nature, possessing spontaneous wettability, whereas films formed from alcohol-only solvents were hydrophobic, and only on conditioning with water were more wettable surfaces attained. This phenomenon was applied in the coating of leukocyte filtration material, where the aqueous-based systems demonstrated lower critical wetting surface tension (CWST) and shorter wetting times relative to both uncoated filters and those coated from alcohol-only systems. The haemocompatibility of the coated filters was equivalent for both coating solvent systems. employed, and far superior when compared to the uncoated control.

Alcohols↗

PubMed2000

A comparison study of the back pain functional scale and Roland Morris Questionnaire. North American Orthopaedic Rehabilitation Research Network.

OBJECTIVE: To determine whether the measurement properties of the Back Pain Functional Scale (BPFS) are superior to the Roland-Morris Questionnaire (RMQ). METHODS: The BPFS and RMQ were administered on multiple occasions to 153 patients with low back pain attending physical therapy. Eleven Canadian clinics and 8 American clinics participated in the study. Ceiling effects, internal consistency, test-retest reliability, cross sectional discriminant validity, and sensitivity to change were investigated. Error estimates in scale points were obtained. RESULTS: A ceiling effect was noted for 6 patients' RMQ scores compared to 3 patients' BPFS scores. Internal consistency for the RMQ and BPFS were 0.87 and 0.93, respectively. The error (95% CI) for a patient's score was +/- 15.5% of the scale range for the RMQ and +/- 10.5% for the BPFS. The test-retest reliability was 0.79 for the RMQ and 0.82 for the BPFS. The error associated with a patient's change score (95% CI) was 27.7% of the scale range for the RMQ and 22.2% for the BPFS. The measures showed similar levels of discriminant validity with respect to physical findings, work status, and education level. The BPFS was more adept at detecting different amounts of change in patients with back pain of less than 2 weeks' duration compared to patients with back pain of 2 or more weeks' duration. CONCLUSION: The BPFS is a competitive functional status measure for patients with low back pain.

Adolescent↗

PubMed1999

Applying the results of self-report measures to individual patients: an example using the Roland-Morris Questionnaire.

Information concerning a patient's functional status is often obtained by asking the patient about activities that cannot be assessed directly in the clinical setting. This information is usually acquired through a verbal exchange between the clinician and patient. The measurement properties of the verbal exchange are unknown. An alternate method of obtaining this information is when patients self-report their functional status. The measurement properties of self-report questionnaires are well known; however, these measures are used infrequently for the evaluation of functional status, progress, and outcome in the clinic. Two reasons are possible for the infrequent use of self-report questionnaires: (1) values obtained from self-report measures have not been used to guide the care of the patient, and (2) a perception exists that these measures take a great deal of time to administer and score. The purpose of this clinical commentary was to describe the application, scoring, and use of a functional status measure (the Roland-Morris Questionnaire) for persons with low back pain and to illustrate how this questionnaire can be efficiently incorporated into clinical practice to aid decision making concerning individual patients. Three patient scenarios are used to illustrate the issues raised in this paper.

Adolescent↗

PubMed1999

The Lower Extremity Functional Scale (LEFS): scale development, measurement properties, and clinical application. North American Orthopaedic Rehabilitation Research Network.

BACKGROUND AND PURPOSE: The purpose of this study was to assess the reliability, construct validity, and sensitivity to change of the Lower Extremity Functional Scale (LEFS). SUBJECTS AND METHODS: The LEFS was administered to 107 patients with lower-extremity musculoskeletal dysfunction referred to 12 outpatient physical therapy clinics. METHODS: The LEFS was administered during the initial assessment, 24 to 48 hours following the initial assessment, and then at weekly intervals for 4 weeks. The SF-36 (acute version) was administered during the initial assessment and at weekly intervals. A type 2,1 intraclass correlation coefficient was used to estimate test-retest reliability. Pearson correlations and one-way analyses of variance were used to examine construct validity. Spearman rank-order correlation coefficients were used to examine the relationship between an independent prognostic rating of change for each patient and change in the LEFS and SF-36 scores. RESULTS: Test-retest reliability of the LEFS scores was excellent (R = .94 [95% lower limit confidence interval (CI) = .89]). Correlations between the LEFS and the SF-36 physical function subscale and physical component score were r=.80 (95% lower limit CI = .73) and r = .64 (95% lower limit CI = .54), respectively. There was a higher correlation between the prognostic rating of change and the LEFS than between the prognostic rating of change and the SF-36 physical function score. The potential error associated with a score on the LEFS at a given point in time is +/-5.3 scale points (90% CI), the minimal detectable change is 9 scale points (90% CI), and the minimal clinically important difference is 9 scale points (90% CI). CONCLUSION AND DISCUSSION: The LEFS is reliable, and construct validity was supported by comparison with the SF-36. The sensitivity to change of the LEFS was superior to that of the SF-36 in this population. The LEFS is efficient to administer and score and is applicable for research purposes and clinical decision making for individual patients.

Activities of Daily Living↗

PubMed1999

The prevalence of low back pain in adults: a methodological review of the literature.

The prevalence of low back pain (LBP) has been reported in the literature for different populations. Methodological differences among studies and lack of methodological rigor have made it difficult to draw conclusions from these studies. A systematic review was done for adult community prevalence studies of LBP published from 1981 to 1998. The technique of capture-recapture was performed to estimate the completeness of the search strategy used. Established guidelines and a methodological scoring system were used to critically appraise the studies. Thirteen studies were deemed methodologically acceptable. Differences in the duration of LBP used in the studies appeared to affect the prevalence rates reported and explain much of the variation seen. It was estimated that the point prevalence rate in North America is 5.6%. Further studies using superior methods are needed, however, before this estimate can be used with confidence to make health care policies and decisions relating to physical therapy.

Adult↗

PubMed1999

Interpreting validity indexes for diagnostic tests: an illustration using the Berg balance test.

Physical therapists routinely make diagnostic and prognostic decisions in the course of patient care. The purpose of this clinical perspective is to illustrate what we believe is the optimal method for interpreting the results of studies that describe the diagnostic or prognostic accuracy of examination procedures. To illustrate our points, we chose the Berg Balance Test as an exemplar measure. We combined the data from 2 previously published research reports designed to determine the validity of the Berg Balance Test for predicting risk of falls among elderly people. We calculated the most common validity indexes, including sensitivity, specificity, predictive values, and likelihood ratios for the combined data. Clinical scenarios were used to demonstrate how we believe these validity indexes should be used to guide clinical decisions. We believe therapists should use validity indexes to decrease the uncertainty associated with diagnostic and prognostic decisions. More studies of the accuracy of diagnostic and prognostic tests used by physical therapists are urgently needed.

Accidental Falls↗

PubMed1998

Comparison of two outcome measures for infants with cerebral palsy and infants with motor delays.

BACKGROUND AND PURPOSE: The purpose of this study was to compare the Gross Motor Function Measure (GMFM) and the Peabody Developmental Gross Motor Scale (PDMS-GM) as measures of change in infants with cerebr-al palsy (CP) and infants with motor delays. We hypothesized that mean change scores would be greater for the GMFM than for the PDMS-GM. SUBJECTS AND METHODS: Subjects were 42 infants with a mean adjusted age of 13.9 months (SD=6.1, range=4.2-24.2). Twenty-four infants had CP, and 18 infants had motor delays. The GMFM and the PDMS-GM were administered to the infants 3 times over a 6-month period. Raw scores were standardized for data analysis. Data were analyzed using a 3-factor repeated-measures analysis of variance. RESULTS: For the 6-month period, mean PDMS-GM age-equivalent scores increased 3.8 months and mean scaled scores increased 35 points for infants with motor delays compared with increased scores of 1.8 months and 13 points for infants with CP. Mean GMFM scores increased by 12.2% for infants with rmotor delays and by 4.2% for infants with CP. The diagnosis X time interaction was significant. Infants with motor delays had a greater change in motor development compared with the infants with CP. The hypothesis that the GMFM is more responsive to change than the PDMS-GM was not supported. CONCLUSION AND DISCUSSION: The findings suggest that the GMFM and the PDMS-GM are comparable in measuring change in infants with CP or motor delays. Implications for selection and use of either measure are discussed.

Analysis of Variance↗

PubMed1998

Sensitivity to change of the Roland-Morris Back Pain Questionnaire: part 1.

BACKGROUND AND PURPOSE: This study estimated the Roland-Morris Back Pain Questionnaire's (RMQ) change score that best classified patients as those who had achieved an important change and those who had not achieved an important change. The study also investigated whether the estimate of change was dependent on patients' initial scores. SUBJECTS AND METHODS: The RMQ was administered to 226 patients with low back pain of less than 6 weeks' duration during their initial visit for physical therapy and following 3 to 6 weeks of treatment. A global rating of change was used to classify patients as those who had changed an important amount and those who had not changed. Receiver operating characteristic curves were used to identify the RMQ change score that most accurately classified patients with respect to important change. This analysis was repeated for 5 overlapping subsamples of patients with initial scores 0 to 8, 5 to 12, 9 to 16, 13 to 20, and 17 to 24. RESULTS: The area under the receiver operating characteristic curves increased when patients' initial scores were taken into account. Estimates of important change were 2, 4, 5, 8, and 8 for the initial score intervals mentioned above. CONCLUSION AND DISCUSSION: Important change appears to be dependent on patients' initial RMQ scores. Subsequent inquiry using different hypotheses would add support to the estimates of important change found in this study.

Adolescent↗

PubMed1998

Sensitivity to change of the Roland-Morris Back Pain Questionnaire: part 2.

BACKGROUND AND PURPOSE: One purpose of this study was to determine whether the Roland-Morris Back Pain Questionnaire (RMQ) could be used to detect clinically meaningful change in individual patients. The construct that served as the basis for this study was that RMQ change scores should be greater for patients meeting their treatment goals than for patients who did not meet their goals. The second purpose of the study was to determine whether sensitivity to change (STC) varies depending on the magnitude of the initial RMQ score. SUBJECTS AND METHODS: Of the 143 patients with low back pain who completed the study, 104 patients achieved their goals and 39 patients did not achieve their goals. Receiver operating characteristic (ROC) curve analysis and likelihood ratios were used to determine the RMQ change scores that best classify patients as having met or not met their goals. RESULTS: The area under the ROC curve for the entire RMQ scale was 0.68, while the curve areas for smaller RMQ intervals varied from 0.80 to 0.97. CONCLUSION AND DISCUSSION: The STC for the entire RMQ scale was poor for the construct examined in this study. The likelihood ratios for smaller RMQ intervals support the construct validity of the RMQ for assessing change in disability. Initial RMQ score magnitudes must be taken into account to improve the rate of making correct predictions about whether meaningful change in disability will occur following treatment.

Adolescent↗

PubMed1998

Use of generic versus region-specific functional status measures on patients with cervical spine disorders.

BACKGROUND AND PURPOSE: Few data exist to support the use of functional status measures on patients with disorders of the cervical spine. This study was designed to compare the construct validity and sensitivity to change of the Neck Disability Index (NDI) and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). SUBJECTS AND METHODS: Patients (N = 146) with a variety of disorders of the cervical spine completed the NDI and the SF-36 prior to treatment. Following discharge from treatment, 69 of these patients completed a second NDI and SF-36. RESULTS: There was evidence for the construct validity and sensitivity to change of the NDI and the physical and mental component scores of the SF-36. The ability of the NDI and SF-36 to detect change varied, depending on the construct tested. The SF-36 was superior in some instances, and the NDI was superior in other instances. The NDI appears to measure both mental and physical health-related factors. CONCLUSION AND DISCUSSION: There appears to be substantial overlap between the 2 measures. The use of both measures, therefore, is probably not necessary. [Riddle DL, Stratford PW. Use of generic versus region-specific functional measures on patients with cervical spine disorders.

Adult↗

PubMed1998

The patient-specific functional scale: validation of its use in persons with neck dysfunction.

Self-report measures of disability are being used more frequently to assess patients' outcomes in clinical practice. This study examines the reliability, validity, and sensitivity to change of the Patient-Specific Functional Scale when applied to persons with neck dysfunction. The Patient-Specific Functional Scale and Neck Disability Index were applied at the initial visit, within 72 hours of the initial visit, and following 1-4 weeks of treatment in 31 patients with cervical dysfunction. At the time of the initial visit, the clinician made an estimate of patients' prognoses on a five-point scale. This estimate served as an priori construct for change: patients with better ratings would change more. The results demonstrate excellent reliability (R = .92) validity (r = .73-.83 compared with the Neck Disability Index, and r = .52-.64 compared with the prognosis rating), and sensitivity of change (r = .79-.83 compared with Neck Disability Index change scores, and r = .46-.53 compared with the prognosis rating). No difference was found between the Patient-Specific Functional Scale and Neck Disability Index in their ability to detect change over time. The results of this study are consistent with previous investigations which have concluded that the Patient-Specific Functional Scale is an efficient and valid measure for assessing disability and change in disability in persons with low back pain and knee dysfunction.

Activities of Daily Living↗