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Biomedical subjects

J M Mitchell

Publications and source records attributed to J M Mitchell.

At least 37 records · Page 2Linked to original sources
PubMed1998

Antimicrobial drug residues in milk and meat: causes, concerns, prevalence, regulations, tests, and test performance.

This paper presents a historical review of antimicrobial use in food animals, the causes of residues in meat and milk, the types of residues found, their regulation in Canada, tests used for their detection, and test performance parameters, with an emphasis on immunoassay techniques. The development of residue detection methods began shortly after the introduction of antimicrobials to food animal production in the late 1940s. From initial technical concerns expressed by the dairy industry to the present public health and international trade implications, there has been an ongoing need for reliable, sensitive, and economical methods for the detection of antimicrobial residues in food animal products such as milk and meat. Initially there were microbial growth inhibition tests, followed by more sensitive and specific methods based on receptor binding, immunochemical, and chromatographic principle. An understanding of basic test performance parameters and their implications is essential when choosing an analytical strategy for residue testing. While each test format has its own attributes, none test will meet all the required analytical needs. Therefore the use of a tiered or integrated system employing assays designated for screening and confirmation is necessary to ensure that foods containing violative residues are not introduced into the food chain.

Animals↗
PubMed1998

Characteristics of the LacTek test as applied to tissue samples: assessment of performance using incurred field samples.

The Lactek test, marketed for antimicrobial residue detection in milk, was validated for the detection of antimicrobial residues in tissues. A previous study found that the LacTek test could confidently identify tissue samples spiked with antimicrobial residues. However, the test could not reliably distinguish violative from nonviolative spiked samples relative to Canadian maximum residue limits (MRLs). The objectives of this study were to assess and compare the performance of the LacTek tests for beta-lactams, tetracyclines, gentamicin, and sulfamethazine on samples containing naturally incurred residues by running the test in parallel with the standard microbial inhibition test (MIT) presently used for the routine testing of tissues at our facility and to assess the agreement with high pressure liquid chromatographic (HPLC) determinative methods. Parallel testing with the official MIT found that the Lactek tests could be confidently used for testing tissue samples containing incurred residues. Among 1,008 MIT-positive samples, the LacTek test found that 90% contained beta-lactams and/or tetracyclines. A further 7.3% of violative residues could not be identified to an antimicrobial class. In addition, 9% of samples testing negative on the MIT were found to contain an antimicrobial residue by the LacTek tests. Comparative testing with HPLC methods found that there was very good agreement between the two tests and that most violations were due to penicillin G and oxytetracycline. Although the LacTek test cannot be used to distinguish violative from nonviolative residue levels, it does offer several advantages over the present MIT. These include speed, ease of use, the ability to identify residues to a specific class, and an improved sensitivity at the MRL level for the most commonly found antimicrobials in tissue.

Anti-Bacterial Agents↗
PubMed1997

Fetal liver length in twin-twin transfusion syndrome.

Fetal liver length was measured by ultrasound in 14 pregnancies with twin-twin transfusion syndrome. The liver size was increased above normal values in both the donor (small) and recipient (large) twin. The liver length was significantly greater than in a control group of dichorionic twin pregnancies with discordant growth. Measurement of liver length may be useful in diagnosing twin-twin transfusion syndrome.

Female↗
PubMed1997

A comparison of resource use and cost in direct access versus physician referral episodes of physical therapy.

BACKGROUND AND PURPOSE: Access to physical therapy in many states is contingent on prescription or referral by a physician. Other states have enacted direct access legislation enabling consumers to obtain physical therapy without a physician referral. Critics of direct access cite potential overutilization of services, increased costs, and inappropriate care. METHODS AND RESULTS: Using paid claims data for the period 1989 to 1993 from Blue Cross-Blue Shield of Maryland, a direct access state, we compiled episodes of physical therapy for acute musculoskeletal disorders and categorized them as direct access (n = 252) or physician referral (n = 353) using algorithms devised by a clinician advisory panel. Relative to physician referral episodes, direct access episodes encompassed fewer numbers of services (7.6 versus 12.2 physical therapy office visits) and substantially less cost ($1,004 versus $2,236). CONCLUSION AND DISCUSSION: Direct access episodes were shorter, encompassed fewer numbers of services, and were less costly than those classified as physician referral episodes. There are several potential reasons why this may be the case, such as lower severity of the patient's condition, overutilization of services by physicians, and underutilization of services by physical therapists. Concern that direct access will result in overutilization of services or will increase costs appears to be unwarranted.

Algorithms↗
PubMed1997

Expenditures on services for persons with acquired immunodeficiency syndrome under a Medicaid home and community-based waiver program. Are selection effects important?

OBJECTIVES: In 1990, the state of Florida implemented an acquired immunodeficiency syndrome (AIDS)-specific Medicaid waiver program to provide home and community-based services to AIDS patients as an alternative to institutional care. The program is available to Medicaid beneficiaries with AIDS who are at risk of institutionalization. This study examines whether the waiver option was effective in reducing Medicaid expenditures per beneficiary during its first 2 years of operation. METHODS: The authors used Medicaid claims data and county information on the availability of health services to model the selection of the waiver option by AIDS patients and then to estimate the effect of the waiver on expenditures controlling for nonrandom program selection. RESULTS: The results indicate that the selection model is highly significant, but that the influence of nonrandom selection on the estimation of the program effects is negligible. More importantly, the regression results indicate that persons with AIDS who use waiver services incur monthly Medicaid expenditures that are on average 22% to 27% lower than otherwise similar nonparticipants. CONCLUSIONS: These results, based on the first 2 years that Project AIDS Care was operational, suggest that home and community-based care for AIDS patients results in lower expenditures per beneficiary.

Adolescent↗
PubMed1997

Access to bone marrow transplantation for leukemia and lymphoma: the role of sociodemographic factors.

PURPOSE: Use of bone marrow transplantation (BMT), a complex, costly treatment for many forms of cancers, has increased significantly in recent years. The increasingly competitive health care marketplace raises concerns about patient access to costly medical procedures such as BMT. We attempted to evaluate patient access to BMT for the treatment of leukemias and lymphomas. METHODS: We analyzed inpatient hospital discharge data from four states (California, Maryland, Massachusetts, and New York) for 2 years (1988 and 1991) to examine whether the use of BMT for patients with either leukemia or lymphoma varies by sociodemographic characteristics and insurance coverage. We developed a sorting algorithm to collapse the discharge data into patient level records. We used logistic regression to analyze the odds of receiving a BMT stratified by disease type (leukemia or lymphoma). RESULTS: After controlling for other factors, black patients with leukemia are 51% to 53% as likely as whites, while black patients with lymphoma are 34% to 45% as likely as white patients to undergo a BMT (P < .05). Medicaid, self-pay patients, and Health Maintenance Organization (HMO) enrollees with either leukemia or lymphoma are significantly less likely to undergo a BMT compared with patients with private insurance. Younger patients are significantly more predisposed to undergo a BMT than older patients. The odds of receiving a BMT have increased over time, but the rates of increase vary by state. Consistent with clinical expectations, the relative odds of BMT vary significantly by type of leukemia or lymphoma. CONCLUSION: Substantial variation exists in access to BMT for patients with either leukemia or lymphoma. Black patients, those enrolled in HMOs, those covered by Medicaid, and self-pay patients were less likely to receive a BMT when admitted for either leukemia or lymphoma. These findings raise concerns about access to cancer treatments for patients in the current health care system.

Black or African American↗
PubMed1996

Strategies to promote the use of advance directives in a residency outpatient practice.

OBJECTIVE: To evaluate patient education and resident education strategies to promote advance directives in the outpatient setting, and to assess barriers to implementation. DESIGN: Controlled clinical trial. SETTING: The internal medicine residents' practice of an urban, university medical center. PATIENTS/PARTICIPANTS: Medical residents and 250 patients seen at least twice in the 3 months prior to the study. INTERVENTIONS: We randomized practice days: one to patient education, one to resident education, and three controls. Resident education consisted of a lecture, a videotape of a model advance directives discussion, and videotaping of an actual discussion by each resident, followed by individual review. Patient education consisted of distributing pamphlets in the waiting room and offering all patients an opportunity to discuss advance directives. MEASUREMENTS AND MAIN RESULTS: We interviewed 187 of these patients (response rate 75%) and surveyed 62 residents (response rate 70%). After 18 months, there were no significant differences in the number of advance directives in charts among the three groups. Documented advance directives discussions with patients in the resident education group increased from 3% to 17% (p < .001), more than those in the patient education (5%) or control group (10%, p = .04). Residents in the resident education group were more likely to report discussing advance directives than those in the patient education or control groups (p = .05). Lack of time (95%) and lack of continuity (76%) were the most frequently cited barriers. In multivariate logistic regression, nonwhite race and non-U.S. birth were negatively associated with patient interest in advance directives. Patient race and birthplace were not associated with actual discussions of advance directives. CONCLUSIONS: Even with intensive efforts to educate outpatients and residents about advance directives, important barriers remain, raising questions about how best to promote advance directives among outpatients.

Adolescent↗
PubMed1996

Urinary excretion profiles of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol in humans after single smoked doses of marijuana.

Interpretation of marijuana-positive urine tests requires an understanding of the excretion pattern of marijuana metabolites in humans. However, limited urinary excretion data from controlled clinical studies of marijuana use are available. In this study, six subjects smoked a single marijuana cigarette (placebo, 1.75% delta 9-tetrahydrocannabinol [THC], or 3.55% THC) each week while residing on the clinical ward of the Addiction Research Center. Individual urine specimens were collected for 7 days after drug administration and analyzed for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH) by gas chromatography-mass spectrometry (GC-MS) with a limit of detection of 0.5 ng/mL. Substantial intersubject variability in patterns of THCCOOH excretion was noted between subjects and between doses. Mean THCCOOH concentrations in the first urine collections were 47 +/- 22.3 ng/mL and 75.3 +/- 48.9 ng/mL after the 1.75 and 3.55% THC cigarettes, respectively. Mean peak urine THCCOOH concentrations averaged 89.8 +/- 31.9 ng/mL and 153.4 +/- 49.2 ng/mL after smoking of approximately 15.8 mg and 33.8 mg THC, respectively. The mean times of peak urine concentration were 7.7 +/- 0.8 h after the 1.75% THC and 13.9 +/- 3.5 h after the 3.55% THC dose. Mean GC-MS THCCOOH detection times for the last positive urine sample after the smoking of a single 1.75 or 3.55% THC cigarette were 33.7 +/- 9.2 h and 88.6 +/- 9.5 h, respectively, when a 15-ng/mL cutoff concentration was used. An average of 93.9 +/- 24.5 micrograms THCCOOH (range, 34.6-171.6 micrograms) was excreted by each subject during the 7-day period after smoking of a single 1.75% THC cigarette. The average amount of THCCOOH excreted in the same time period after the high dose was 197.4 +/- 33.6 micrograms (range, 107.5-305.0 micrograms). This represented an average of only 0.54 +/- 0.14% and 0.53 +/- 0.09% of the original amount of THC in the low-and high-dose cigarettes, respectively. These data provide a detailed complication of THCCOOH concentrations in urine after administration of marijuana that may aid in the interpretation of urine cannabinoid results.

Adult↗
PubMed1996

Provider assessments, the uninsured, and uncompensated care: Florida's Public Medical Assistance Trust Fund.

Several states have imposed a provider tax to create a revenue pool for compensating hospitals that provide services to the uninsured. In Florida, this fund, called the Public Medical Assistance Trust Fund, has been at least partially successful: First, fund dollars have helped provide coverage to many previously uninsured persons. Second, although direct subsidy payments cover only a small share of prior year uncompensated care dollars, public hospitals appear to be the primary beneficiaries of the subsidy payments. Third, the provider tax yields a stable, albeit inadequate, source of revenue. It appears to be a useful tool for generating the initial funding to expand health insurance coverage, but in order to raise enough money to finance substantial change, provider assessments will have to be imposed on a wider range of health care facilities and even on certain types of health care professionals.

Florida↗
PubMed1995

Physician ownership of ancillary services: indirect demand inducement or quality assurance?

This paper analyzes two competing explanations for the ownership of ancillary facilities by referring physicians: indirect demand inducement and quality assurance. Consistent with the demand-inducement explanation we find physician-owned clinics treat patients for 50 percent more visits than do independent clinics and the differential is directly related to factors facilitating demand inducement. We find no difference in quality of care across ownership structures, however. In further support of the demand-inducement hypothesis we find that physical therapists are less likely to work in physician-owned clinics in states where therapists are allowed to practice independently.

Ambulatory Care Facilities↗
PubMed1995

Short fourth toes in Rett syndrome: a biological indicator.

Classic Rett syndrome is now well-known as a non-dysmorphic developmental disorder almost certainly of genetic origin. Short 4th toe (uni- or bi-lateral) is inherited as an autosomal dominant with 27% penetrance and is found also in certain dysmorphic syndromes. Having observed the anomaly in several Rett cases, we examined a cohort of classic Rett people at advisory clinics and all the residents in an adult learning disabled hospital in order to determine the significance of the association. Among the Rett clinic group 28 of 137 showed the anomaly (20%). Among the heterogeneous hospital group it was found in 19 of 526 people, 9 of 206 females (4%) and 10 of 320 males (3%). Rett syndrome was present in 7% of all the women (14 of 206 women). Four of the Rett women showed the toe anomaly (28% of the Rett cases). The anomaly was found in 4 men and 4 women with Down syndrome, representing 16% (8 of 49). Diagnoses in other men with the anomaly included foetal alcohol syndrome, toxoplasmosis, 18/2 translocation and birth injury. The only other woman with the anomaly was profoundly disabled with short limbs. The strong positive association of the anomaly with Rett syndrome and Down syndrome throws new light on the developmental processes affected by these diseases.

Brain↗
PubMed1995

Detection times of marijuana metabolites in urine by immunoassay and GC-MS.

Reports of prolonged drug excretion have provided the basis for the common assumption that cannabinoid metabolites may he detected in urine for a week or longer. The accuracy, sensitivity, and specificity of immunoassays for the detection of cannabinoids and metabolites are unique for a specific assay and may change overtime. it is important that individuals who select assays and those who interpret test results be aware of qualitative and quantitative changes that occur. In the present study, detection times of cannabinoids in urine were determined using cannabinoid immunoassays with 20-, 50-, and 100-ng/mL cutoffs and using gas chromatography-mass spectrometry (GC-MS). Six subjects each smoked a single marijuana cigarette (placebo, 1.75, or 3.55% delta9-tetrahydrocannabinol [THC]) each week while residing on the clinical ward of the Addiction Research Center. Each urine specimen was analyzed under blind conditions by immunoassay according to the manufacturer's instructions. The following cannabinoid reagents were evaluated: EMIT d.a.u. 100, EMIT d.a.u. 50, EMIT d.a.u. 20, EMIT II 100, EMIT II 50, Abuscreen OnLine, and Abuscreen RIA, DRI, and ADx. All urine specimens were also analyzed for 11-nor-9-carboxy-delta9-THC by GC-MS using a 15-ng/mL cutoff. Urinary cannabinoid detection times varied substantially across assays, subjects, doses, and cutoff concentrations. Detection times were shorter than previously assumed. Mean detection times increased from a maximum of 0.5 days after the low dose to 1.5 days after the high dose using the 100-ng/mL cutoff. Mean detection times were less than 1 day following the low dose and less than 2 days following high-dose exposure using the 50-ng/mL cutoff. Mean detection times ranged from 1 to 5 days after the low dose and from 3 to 6 days after the high dose using the 20-ng/mL cutoff immunoassay. GC-MS detection times were approximately twice as long as mean detection times using an immunoassay with a cutoff of 50 ng/mL. Differences in sensitivity and specificity between the available immunoassay products affected the efficiency of detection of marijuana use. These results indicate that recent reductions in cannabinoid cutoffs by military and federally mandated programs will increase detection times and improve sensitivity, as expected. However, monitoring acute marijuana usage with a commercial cannabinoid immunoassay that has a 50-ng/mL cutoff concentration provides only a narrow window of detection of 1-2 days.

Adult↗
PubMed1995

Ownership and utilization of MR imagers in the Commonwealth of Virginia.

PURPOSE: To assess distribution, operation, and ownership of magnetic resonance (MR) imagers in Virginia in 1991. MATERIALS AND METHODS: Questionnaires regarding ownership, location, hours of operation, annual throughput, sources and amounts of revenue, and expenses were mailed to identified providers. Data, specifically regarding ownership and location, were analyzed. RESULTS: Staff from 95% of MR facilities responded. Most facilities were located in and around major metropolitan areas. Population density per imager ranged from one per 76,000 to one per 222,000 persons. Imagers in larger metropolitan areas were operated for longer hours with higher revenues and greater expenses than were those in lower-population-density areas. Imagers owned by physicians in a position to self-refer had the highest patient throughput, the most revenue, and a much lower percentage of revenues from Medicare and Medicaid than did other ownership types. CONCLUSION: Patient access to MR services in Virginia is inhomogeneous. Important aspects of utilization are location and ownership. Ownership by physicians who can self-refer is associated with higher use, greater overall revenues, and less service to the poor and elderly.

Costs and Cost Analysis↗
PubMed1995

Florida's Medicaid AIDS waiver: an assessment of dimensions of quality.

Some State Medicaid agencies have implemented home and community-based waiver programs targeting acquired immunodeficiency syndrome (AIDS) patients. Under these initiatives, State Medicaid agencies can provide home and community-base services to persons with AIDS (PWA) as an alternative to more costly Medicaid-covered institutional care. This article evaluates quality of care under the Florida Medicaid waiver for PWA along two dimensions: program effectiveness and client satisfaction. Clients are generally satisfied with their case managers and the range and availability of services. Case managers appear to be well trained. Moreover, the probability of turnover is quite low, despite heavy caseloads and high mortality. The major difficulty faced by clients adn case managers relates to the process of becoming Medicaid eligible.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Transabdominal versus transvaginal ultrasound in the diagnosis of polycystic ovaries in a population of randomly selected women.

A study was conducted which compared transvaginal and transabdominal ultrasound in determining the prevalence of polycystic ovaries in a population of women. Women, chosen randomly from electoral rolls, were sent a letter inviting them to take part in a study determining the presence of polycystic ovaries. A transvaginal and transabdominal ultrasound scan was performed on day 5-9 of their menstrual cycles. A total of 187 women (mean age 33 years) took part in the study. The prevalence of polycystic ovaries was 21% (40/187) by transabdominal ultrasound and 27% (36/134) by transvaginal ultrasound. No differences existed between women with polycystic and normal ovaries with respect to uterine size and endometrial thickness. Mean ovarian volume was larger in women with polycystic ovaries irrespective of the use of hormonal contraception or breast feeding. There was no difference in the prevalence of polycystic ovaries diagnosed by transabdominal or transvaginal ultrasound in the group of randomly selected women. However, almost 20% of the women declined a transvaginal ultrasound examination.

Journal Article↗