Ophthalmic services research: towards increasing the role of economic and operations research methods in the delivery of eye care services.
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Delivery of Health Care↗
Biomedical subjects
A F Smith
Publications and source records attributed to A F Smith.
Current and possible screening practices for diabetic retinopathy by general practitioners: new evidence from a pilot survey of Oxfordshire general practitioners.
AIM: To investigate the relationship between the number of general practitioners in a GP practice and screening for diabetic retinopathy in order to evaluate the viability of increased GP involvement in screening for blinding diabetic eye disease. METHOD: A ten point questionnaire was developed and sent to 50 randomly selected general practitioner practices throughout Oxfordshire. 41 (82%) of the general practitioner practices returned completed questionnaires. RESULTS: The mean number of GP's per GP practice was 4, with a standard deviation of 4 GP's while GP practice sizes ranged from 1 to 9 GP's per practice. Overall, 66% (n = 27) of GP practices indicated that they referred their diabetic patients for screening, even though 83% (n = 34) of GP practices performed funduscopy. 76% (n = 31) of GP practices ran diabetic clinics, and 66% (n = 27) of GP practices indicated that they wanted more training in the use of the ophthalmoscope and detecting diabetic retinopathy, despite the fact that 78% (n = 32) of this same group had received some form of postgraduate medical training in diabetes in the last five years. Lastly, only 27% (n = 11) of GP practices would alter their attitude to screening for diabetic retinopathy if they were paid substantially more to do so. CONCLUSIONS: Most GP practices referred their diabetic patients for screening, even though the majority of GP practices performed some form of funduscopy and that amongst the largest GP practice sizes all performed dilated funduscopy and did not refer for screening. Given sufficient remedial training in the use of the ophthalmoscope and practical sessions on detecting diabetic retinopathy, it is likely that smaller GP practice sizes would be encouraged to screen for sight-threatening diabetic retinopathy.
Data Collection↗
How children remember what they have eaten.
OBJECTIVES: To determine whether students could verbalize, within 1 1/2 hours, how they remembered items eaten at the school lunch; to determine whether the categories of self-reported retrieval mechanisms were similar for two interview styles, integrated and nonintegrated; and to determine the effect of the two interview style on the accuracy of reporting items eaten by comparing reports with direct observation. DESIGN: Two styles of dietary intake interviews were compared with observed intake in a school lunch setting. SETTING: Two elementary schools in Georgia. SUBJECTS/SAMPLES: Eighty-two of 106 fourth graders from four classes volunteered; 24 (six per class) were randomly selected and assigned to an interview style. Students interviewed using a nonintegrated style verbalized how they remembered after they had reported everything eaten. Students interviewed using an integrated style verbalized how they remembered at the same time they reported eating each item. Both interview styles included free report followed by prompted report. MAIN OUTCOME MEASURES: Reported retrieval mechanisms were coded into 13 categories. Five measures of performance (specific match rate, general match rate, intrusion rate, omission rate, and overall match rate) were calculated by interview style for free report and prompted report separately. STATISTICAL ANALYSES PERFORMED: We analyzed the effect of interview style on the number of students reaching 100% accuracy after prompting and on accuracy of reporting condiments using Fisher's exact test. RESULTS: Most students could articulate how they remembered items eaten. Reported retrieval mechanism categories were comparable for both interview styles. Visual imagery, usual practice, behavior chaining, and preference were the most commonly reported retrieval mechanisms. Accuracy of free reports did not differ by interview style; however, the nonintegrated interview style produced dietary self-reports with fewer condiment omissions during free report and higher accuracy after prompting. APPLICATIONS: Determining what retrieval mechanisms children commonly use for remembering items eaten may help researchers design cues to improve the accuracy of dietary self-reports. More accurate dietary self-reports could markedly affect the many types of research that use dietary assessment.
Child↗
Exchangeable apolipoproteins of insects share a common structural motif.
Elucidation of the secondary structure of the exchangeable apolipoproteins has been hindered by the difficulty in producing crystals suitable for X-ray spectrographic analyses. Consequently, in order to analyze potential structure-function relationships in the family of insect exchangeable apolipoproteins, apolipophorins-III (apoLps-III), two apoLps-III cDNA clones, one from the palo verde beetle (Derobrachus geminatus) and one from the house cricket (Acheta domesticus), have been isolated and sequenced. Multiple sequence alignments of the deduced protein sequences with two previously reported apolipophorins-III from Manduca sexta and Locusta migratoria reveal low sequence identity, suggesting that these proteins are very old and are highly divergent. Computer-assisted predictions of protein structure and subsequent analyses, using the known secondary structure of Locusta migratoria apolipophorin-III as a control, indicate that these insect proteins are composed of five amphipathic helices with characteristics similar to those of the helical domains of the mammalian exchangeable apolipoproteins. Thus, although insect and vertebrate exchangeable apolipoproteins share a common function in assisting lipid transport, precise amino acid identity is less important than the common structural feature of multiple amphipathic helices. Moreover, because these proteins occur widely among insect species, even in those where flight is limited or absent, we hypothesize that apolipophorin-III has a more generalized function in lipid metabolism than had been previously proposed.
Amino Acid Sequence↗
Bayesian inference in multipoint gene mapping.
The problem of ordering and mapping genes on the basis of recombinant data and radiation hybrid data is formulated as a problem of Bayesian inference for an unknown permutation. The challenging computational problems posed by this approach are shown to be resolvable using Markov chain Monte Carlo methods.
Algorithms↗
Cognitive psychological issues of relevance to the validity of dietary reports.
All dietary assessment methods engage the cognitive processes of respondents, requiring them to retrieve and report information from memory. I first discuss the distinction between daily and frequency methods of dietary assessment: from a psychological perspective, the essential distinction between these classes of methods is in the cues that are provided for retrieval of information rather than the length of the reference period or the specificity of the information to be retrieved. I then review selectively psychological research on aspects of cognition that are central to dietary reporting; chief among these are the nature of the representation of dietary information in memory and the fidelity of frequency judgments. I conclude by describing several potential areas for collaborative research between cognitive psychologists and nutritional epidemiologists. The ability of respondents to provide data must be considered in the design and selection of dietary assessment methods.
Cognition↗
Crystallization, structure determination and least-squares refinement to 1.75 A resolution of the fatty-acid-binding protein isolated from Manduca sexta L.
The molecular structure of an insect fatty-acid-binding protein isolated from Manduca sexta L. has been determined and refined to a nominal resolution of 1.75 A. Crystals used in the investigation were grown from 1.6 M-ammonium sulfate solutions buffered at pH 4.5 with 50 mM-sodium succinate, and belonged to space group P2(1) with unit cell dimensions of a = 27.5 A, b = 71.0 A, c = 28.7 A and beta = 90.8 degrees. An electron density map, phased with four heavy-atom derivatives and calculated to 2.5 A resolution, allowed for complete tracing of the 131 amino acid residue polypeptide chain. Subsequent least-squares refinement of the model reduced the R-factor from 46.0% to 17.3% using all measured X-ray data from 30.0 A to 1.75 A. Approximately 92% of the amino acid residues fall into classical secondary structural elements including ten strands of anti-parallel beta-pleated sheet, two alpha-helices, one type I turn, three type II turns, four type II' turns and one type III turn. As in other fatty-acid-binding proteins, the overall molecular architecture of the insect molecule consists of ten strands of anti-parallel beta-pleated sheet forming two layers that are nearly orthogonal to one another. A helix-turn-helix motif at the N-terminal portion of the protein flanks one side of the up-and-down beta-barrel. The functional group of the fatty acid is within hydrogen-bonding distance of Gln39, Tyr129, Arg127 and a sulfate molecule, while the aliphatic portion of the ligand is surrounded by hydrophobic amino acid residues lining the beta-barrel. The binding of the carboxylic acid portion of the ligand is very similar to that observed in P2 myelin protein and the murine adipocyte lipid-binding protein, but the positioning of the hydrocarbon tail after approximately C6 is completely different.
Animals↗
Isolation, characterization, and cDNA sequence of two fatty acid-binding proteins from the midgut of Manduca sexta larvae.
Two abundant fatty acid-binding proteins (MFB1 and MFB2) were isolated from the midgut cytosol of larval Manduca sexta. As isolated, MFB1 and MFB2 were found to contain bound fatty acids in a 1:1 molar stoichiometric ratio. Immunological screening demonstrated that MFB1 and MFB2 were restricted to the midgut in a gradient distribution, with MFB1 more concentrated in the anterior two-thirds of the midgut and MFB2 more concentrated in the posterior two-thirds of the midgut. MFB1 exchanged fatty acid more readily than did MFB2. MFB1 was about 2% and MFB2 about 12% of the cytosolic protein in the midgut. cDNA clones for MFB1 and MFB2 both encode proteins of 131 amino acids that are rich in lysine and acidic residues. Analysis of the amino acid sequence alignment of the MFBs with six mammalian fatty acid-binding proteins revealed a number of shared features: 9 conserved glycines, presumably important in turns of the beta-strands; a basic amino acid in a position corresponding to the residue reported to participate in binding the carboxyl group of the fatty acid (Arg in MFB1 and Lys in MFB2); and conservation of many of the residues important in binding the aliphatic portion of the fatty acid.
Amino Acid Sequence↗
Unitary classification in a comparison task.
Sequential effects were used to diagnose whether elements in a two-object comparison task are represented as a perceptual unit or separately. The presence of sequential effects and absence of influences of individual elements on the subsequent trial in a successive comparison task favor the hypothesis that the elements in a pair are represented as a unit, and that a response is made to the perceptual unit. The patterns of response times on same and different trials differed in several ways; these suggested that the quality of the representations of same and different trials may differ.
Adult↗
Question-induced cognitive biases in reports of dietary intake by college men and women.
In two experiments, investigated how variations in questionnaire structure influence respondents' reports of two aspects of dietary intake--the frequency with which various food items are eaten and the sizes of the portions that are eaten. In Experiment 1, approximately 400 subjects, prior to making a frequency judgment, were asked to think either about a specific occasion or about all the occasions on which they had eaten a particular food. The thoughts that preceded the frequency judgment influenced that judgment: Thinking of the range of occasions on which a food is consumed resulted in higher frequency estimates than thinking only of the most recent occasion. In Experiment 2, the same subjects made judgments about their typical portion sizes of several foods relative to described standards. For only one of eight foods were estimates properly and significantly affected by differences among the described standards. These results suggest that respondents are not particularly sensitive to portion-size definitions. We consider the implications of these phenomena for the development of a general theory of the cognitive processes that subserve health-survey responding.
Adult↗
Tomato pills will cure all your ills.
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History, Ancient↗
Multiple forms of alkaline phosphatase in plasma of hemodialysis patients.
We used quantitative assays to measure the activity of the bone, liver, and intestinal forms of alkaline phosphatase in plasma in 75 patients with endstage chronic renal failure undergoing hemodialysis. The results were correlated with radiological and other biochemical indices of bone disease and with biochemical indices of liver disease. The total activity of alkaline phosphatase in plasma increased in 28 patients. In 10 of these patients, nine of whom had increased activity of gamma-glutamyltransferase in plasma, the increase in total activity of alkaline phosphatase was from the liver isoenzyme alone (nine patients) or from the liver and bone isoenzymes together (one patient). Intestinal alkaline phosphatase in plasma, although greater than 23 U/L in eight patients, was solely responsible for the increase in total alkaline phosphatase in one patient (who had normal gamma-glutamyltransferase). Bone alkaline phosphatase in plasma was increased in 25 patients, seven of whom had normal total alkaline phosphatase, and was closely correlated (r = 0.78) with osteocalcin concentration in plasma, which was increased in a much greater proportion of patients (99%). Both total and bone alkaline phosphatase were correlated with parathyrin in plasma (r = 0.46 and 0.50, respectively) and with osteocalcin (r = 0.60 and 0.78, respectively). Osteocalcin and bone alkaline phosphatase, but not parathyrin, decreased with age, implying that the skeletal response to parathyrin may be age dependent. In patients with increased total alkaline phosphatase undergoing hemodialysis, the concurrent measurement of gamma-glutamyltransferase may help identify whether the enzyme increase originates from the liver or bone, but this approach wrongly identified the source of the increase in three of 28 patients. Therefore, we recommend a separate measurement of the bone isoenzyme of alkaline phosphatase.
Adolescent↗
Estimation of relative potency with sequential dilution errors in radioimmunoassay.
Sequential dilution is a very common procedure in radioimmunoassay, in which the dilution error will be accumulated from the highest to the lowest concentration. A simulated example in relative potency determination is used to demonstrate the potentially wrong conclusion that can be drawn, when the dilution error is not properly included in the model. A Bayesian method is used and an alternative approximation via maximum likelihood is proposed. An alternative experimental design is recommended to increase the precision of the inference.
Bayes Theorem↗
Inter-relationships between selenium and thyroid hormone metabolism in the rat and man.
Labelling of rat kidney microsomes in vitro with [125I]-bromoacetyl T4 produced two bands on SDS/PAGE with Mr of 55 kDa and 27.5 kDa representing protein disulphide isomerase and type I iodothyronine deiodinase (ID-I) respectively. The amount of the 55 kDa band was unchanged by selenium (Se) deficiency but the 27.5 kDa protein was markedly decreased in kidney microsomal fraction obtained from Se-deficient rats. Concurrent Se and iodine deficiency produced a significant increase in thyroid weight, plasma thyrotrophin (TSH) and a decrease in thyroidal iodine when compared with either single Se or iodine deficiency. These results suggest that ID-I is a selenoprotein and that Se deficiency can exacerbate the hypothyroidism observed in iodine deficiency. In man, blood glutathione peroxidase and blood Se levels were decreased in hyperthyroidism due to Graves' disease whilst normal levels of these analytes were found in patients treated for Graves' disease. These results suggest that thyroid status can affect Se balance rather than Se deficiency predisposes to Graves' disease.
Animals↗
Can prepregnancy care of diabetic women reduce the risk of abnormal babies?
OBJECTIVE: To see whether a prepregnancy clinic for diabetic women can achieve tight glycaemic control in early pregnancy and so reduce the high incidence of major congenital malformation that occurs in the infants of these women. DESIGN: An analysis of diabetic control in early pregnancy including a record of severe hypoglycaemic episodes in relation to the occurrence of major congenital malformation among the infants. SETTING: A diabetic clinic and a combined diabetic and antenatal clinic of a teaching hospital. PATIENTS: 143 Insulin dependent women attending a prepregnancy clinic and 96 insulin dependent women managed over the same period who had not received specific prepregnancy care. MAIN OUTCOME MEASURE: The incidence of major congenital malformation. RESULTS: Compared with the women who were not given specific prepregnancy care the group who attended the prepregnancy clinic had a lower haemoglobin AI concentration in the first trimester (8.4% v 10.5%), a higher incidence of hypoglycaemia in early pregnancy (38/143 women v 8/96), and fewer infants with congenital abnormalities (2/143 v 10/96; relative risk among women not given specific prepregnancy care 7.4 (95% confidence interval 1.7 to 33.2]. CONCLUSION: Tight control of the maternal blood glucose concentration in the early weeks of pregnancy can be achieved by the prepregnancy clinic approach and is associated with a highly significant reduction in the risk of serious congenital abnormalities in the offspring. Hypoglycaemic episodes do not seem to lead to fetal malformation even when they occur during the period of organogenesis.
Ambulatory Care Facilities↗
Alkaline phosphatase isoenzymes in plasma in hyperthyroidism.
Alkaline phosphatase (ALP; EC 3.1.3.1) isoenzymes were measured in the plasma of 63 untreated hyperthyroid patients (the hyperthyroid group), 58 treated hyperthyroid patients, and 100 blood donors. Total, liver, and bone ALP activities were significantly higher in the hyperthyroid group than in the treated hyperthyroid group or the blood donors. Bone ALP was more frequently and more markedly abnormal than liver ALP. Intestinal ALP did not differ significantly between the groups. The hyperthyroid patient group had significantly higher plasma calcium concentrations and lower serum parathyrin concentrations than those of the treated hyperthyroid group.
Adult↗
Plasma alkaline phosphatase isoenzymes in diabetes mellitus.
Alkaline phosphatase (ALP) isoenzymes were measured in type 1 diabetics, type 2 diabetics and in a non-diabetic control group. Within the diabetics and the control group, intestinal ALP activity was significantly higher in BO secretors than A secretors or ABO non-secretors. There was no difference in intestinal ALP activity between type 1 and type 2 diabetics but the diabetics had a significantly higher activity of this isoenzyme than the corresponding blood group/secretor status category of the control group. Liver ALP was significantly higher in the diabetics compared with the control group. Bone ALP showed no significant difference between the diabetics and the control group.
Adult↗
Comparison of fructosamine with glycosylated hemoglobin and plasma proteins as measures of glycemic control.
The relative value of fructosamine as an alternative to glycosylated hemoglobin (HbA1) and other measures of glycemic control was assessed in 100 insulin-dependent (IDDM) and 104 non-insulin-dependent (NIDDM) diabetic patients. We measured HbA1 (by electrophoretic and affinity methods), plasma glucose, glycosylated plasma proteins, and fructosamine in blood taken at a single clinic visit. The values were compared both by correlation analysis and by considering whether the various indices of glycemic control placed the patients in the same clinical decision categories as they were in by the HbA1 (affinity) result. Fructosamine correlated moderately well with HbA1 (affinity; r = .8) and placed 71% of IDDM and 72% of NIDDM patients in the same clinical category of good, moderate, or poor control. Differences can probably be partly attributed to the different periods over which HbA1 and fructosamine reflect average glycemia and partly to imprecision.
Adolescent↗