Biomedical subjects
Paul L Padfield
Publications and source records attributed to Paul L Padfield.
Assessing the HPA axis in patients with pituitary disease: a UK survey.
OBJECTIVE: Assessing the integrity of the hypothalamic-pituitary-adrenal (HPA) axis following pituitary surgery is necessary to determine the requirement for glucocorticoid replacement therapy, but there remains controversy about the optimum way to measure this. DESIGN AND MEASUREMENTS: Postal questionnaire survey among UK endocrinologists to evaluate the current methods used. RESULTS: The response rate was low (81 out of 598 questionnaires mailed), although 85% were consultants. Fifty-five percent measured 9:00 h plasma cortisol in the immediate postoperative phase. Most carried out definitive testing between 4 and 12 weeks: 36% routinely used the insulin tolerance test (ITT), 59% used the short synacthen test (SST). The 30-min cortisol value was used by 67% as a 'pass' when interpreting the results. Others included cortisol measurement at 60 min (17%) or incremental value (7%). For long-term follow-up of patients not rendered ACTH-deficient by surgery, 64% used the SST for patients who had received radiotherapy. If patients had not had radiotherapy, 42% used the SST, whereas 33% did no routine testing unless the patient was symptomatic or there was evidence of tumour recurrence on imaging. If patients were symptomless but 'failed' the chosen test, 28% still treated the patient with glucocorticoid replacement, 38% retested before treatment and 24% recommended glucocorticoid cover for when unwell or 'stressed'. Fifty-six percent used hydrocortisone at doses of 20 mg/day as replacement therapy. CONCLUSION: Thus, assessment of the HPA axis remains controversial. Although the SST is becoming more popular, there is still considerable variation in the interpretation of results and, in particular, the decision of whether or not to treat with lifelong glucocorticoid replacement therapy.
Do SpaceLabs ambulatory non-invasive blood pressure recorders measure blood pressure consistently over several years use?
OBJECTIVE: To assess the measurement consistency of SpaceLabs ambulatory recorders (Spacelabs, Washington, USA) that are in regular use. METHODS: A total of 14 SpaceLabs 90207 and one 90217 ambulatory recorders were tested for measurement consistency using the Dynatech CuffLink (Dynatech, Nevada, USA), a commercially available non-invasive blood pressure (NIBP) simulator. The NIBP recorders were tested at a range of pressures with 20 repeated determinations at a simulated 120/80 mmHg and five repeated determinations at simulated pressures of 80/50, 100/80, 150/100, 200/165 and 250/195 mmHg. Tests were carried out in 1998, 2002 and late 2003 or early 2004. CONCLUSIONS: All 15 SpaceLabs recorders measured consistently over the 6 years with 89.5% of the differences in average pressures, recorded by any particular device at each recorded pressure, less than 2 mmHg between successive test episodes. The maximum difference was 4.5 mmHg and 60.1% of the differences were less than 1 mmHg. The measurements for all devices were within the tolerances specified by the supplier for the device when tested with the simulator. Maintenance records also show that most devices required breakdown maintenance less than once every 3 years. The results show that the SpaceLabs devices maintain measurement consistency in the demanding conditions of ambulatory pressure recording over several years.
Parathyroid hormone and hypertension.
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Self monitoring of blood pressure at home.
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Prevalence and role of a raised aldosterone to renin ratio in the diagnosis of primary aldosteronism: a debate on the scientific logic of the use of the ratio in practice.
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Ten years on: Safety of short synacthen tests in assessing adrenocorticotropin deficiency in clinical practice.
Since 1988, when a retrospective study of patients attending this unit was published, we have advocated the use of the short synacthen test (SST) as the primary screening investigation to detect ACTH deficiency. However, others have published comparisons of SST and insulin tolerance tests that suggest a significant false negative rate with SST, leading to concern that some patients who pass the SST are in danger from the clinical consequences of ACTH deficiency. To address this, we audited biochemical results and clinical outcome in 63 patients who did not have ACTH deficiency detected (i.e. who passed the test) by SST after pituitary surgery. Twelve of the 63 patients who passed a SST after pituitary surgery became ACTH-deficient later as diagnosed by SST: 4 within the first year, 2 of whom had received postoperative radiotherapy (3 had symptoms of tiredness and 1 was admitted to the hospital with a viral infection); 8 in yr 3-5, 7 of whom had received postoperative radiotherapy (all had either no symptoms or symptoms of tiredness alone). Thus, the predictive value of the SST in excluding ACTH deficiency is approximately 97% (2 of 63 patients who initially passed the SST were found to be ACTH-deficient within 12 months without having received postoperative radiotherapy). Only 1 patient was ill enough to require hospital admission. Setting the risk of false negatives with SST against the morbidity and manpower implications associated with insulin tolerance tests, SST remains the primary screening test for ACTH deficiency in our practice. However, a high index of clinical suspicion to detect false negative results must be maintained.
[Three simple steps for improving diagnostic accuracy in hypertension.].
OBJECTIVE: Most patients have only had three measurements of blood pressure before being labelled as hypertensive. This abbreviated assessment may lead to inaccurate classification, unnecessary treatment and dilution in treatment benefit for the population. We aimed to explore how accurate current methods are in diagnosing mild hypertension, and to explore practical methods of improving targeting of antihypertensive treatment using clinic visits but without lengthy observation. MATERIAL AND METHODS: We applied current diagnostic methods to 3965 individuals with mild hypertension who were followed for a year in the placebo arm of the MRC Mild Hypertension Trial (Medical Research Council). We thus calculated the proportion selected for treatment by current methods and the diagnostic accuracy, using average blood pressure beyond six months as representing "true" long-term blood pressure. We looked at the benefit of averaging blood pressures, prolonging observation modestly and estimating within-person blood pressure variability. RESULTS: Prolonging observation to three months selects a smaller (by about 12%) proportion of the sample for treatment. At three months the proportion of the sample selected is similar to the proportion defined as "truly" hypertensive. The diagnostic accuracy of current methods is poor with up to 69% discrepancy in classification. This discrepancy was improved in absolute terms by up to 18% by prolonging observation to three months and using average blood pressures. Identifying those individuals with low within-person variability allows marked improvement in the prediction of "true" hypertension. CONCLUSION: Although some inaccuracy in the diagnosis of hypertension is inevitable, observation for three months, averaging blood pressures and estimating within-person blood pressure variability can markedly improve upon current methods used for targeting antihypertensive treatment.
Self-monitored blood pressure: a role in clinical practice?
Electronic self-monitoring of blood pressure is increasing in popularity and most international guidelines on the management of hypertension approve cautious use of the technique in the assessment of potentially hypertensive individuals. A recent editorial in the Archives of Internal Medicine suggested that it was "appropriate to encourage the widespread use of self recorded BP as an important adjunct to the clinical care of the patient with hypertension". Such a statement is based on increasing evidence that self-monitoring of blood pressure gives similar information to daytime ambulatory blood pressure -- a now well-established technology in the management of hypertension. Suggested strategies for the use of self-monitoring of blood pressure include monitoring in individuals whose clinical risk status is low enough that they need not necessarily be given medical therapy simply on the basis of a clinic pressure (i.e. at a 10 year risk of cardiovascular disease below 20%). The threshold for defining 'normotension/hypertension' is now regarded as being broadly similar for ABPM and SBPM and is set at 135/85 mmHg. In a recent meta-analysis of all available studies the average difference between these techniques, using the same patients, is -1.7/1.2 mmHg. There is some evidence that careful use of self-monitoring may improve blood pressure control in patients who are otherwise resistant to care. Self-monitoring of blood pressure has now been shown in at least one major prospective study to predict outcome better than clinic pressures and in that setting it now has equivalence to the use of ABPM. There remain issues regarding the availability of validated devices, the quality of training of patients in their use and the possibility that inaccurate recording might occur, either deliberately or by accident. Self-monitoring of blood pressure may well not give the same readings as carefully measured blood pressure by research nurses but its use is clearly superior to routine clinical practice. The technique is ripe for widespread application.