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Biomedical subjects

M J O'Doherty

Publications and source records attributed to M J O'Doherty.

At least 91 records · Page 5Linked to original sources
PubMed1996

Hepatitis A vaccine responses in HIV-positive persons with haemophilia.

The safety and immunogenicity of subcutaneously (s.c.) administered hepatitis A (HA) vaccine was evaluated in HIV positive and negative patients with haemophilia and healthy male controls. The vaccine was well tolerated. Seroconversion occurred among all controls after one dose of vaccine but was delayed among patients, particularly if HIV-positive-4 of 17 (24%) failed to respond to three doses of vaccine. Following the third dose of vaccine, geometric mean titres were significantly higher among controls (1354) than among HIV infected patients (204) (P < 0.05). Non-responders failed to develop an immune response following boosting with high titre vaccine. Patients with haemophilia may be vaccinated against HA s.c. but consideration should be given to ensuring that HIV-positive individuals with haemophilia and other immunosuppressed individuals should have their immune responses checked since additional booster doses or passive prophylaxis may be necessary in such individuals.

Adolescent↗
PubMed1996

Assessment of changes in dual-energy X-ray absorptiometry performance following a system upgrade.

System upgrades are a constant feature of many highly technical specialties and are normally assumed to have a negligible effect on patient data. We report on the assessment of an upgrade made to a Norland XR-26 dual-energy X-ray absorptiometry (DXA) system. The upgraded version (2.3) consisted of new hip positioning aids, hip image analysis software and updates to the normal ranges. Measurements of femoral neck and trochanteric bone mineral density correlated well between versions (r = 0.969 and r = 0.971), those for femoral neck and trochanteric bone mineral content less well (r = 0.956 and r = 0.911), and Ward's triangle values and femoral neck area measurements were poorly correlated (r = 0.719-0.881). The upgrade was claimed to improve precision while reducing analysis and imaging time. Improved precision was not demonstrated, with good precision found both before and after the upgrade. Correlation between femoral neck Z-scores were good for the European normal range (r = 0.970), but unacceptable for the UK range (r = 0.769). These correlations were not close enough to allow patients scanned with the old version to be followed up with scans using the upgrade. The upgrade was, however, preferred for new attenders because of the improved speed and automation of hip analysis, without loss of precision. The most important implication in terms of patient management was the change made to the UK normal range, which had a very large effect on the number of patients deemed to be at risk from osteoporosis. It is essential that any upgrade introduced to an existing DXA system is carefully evaluated, since it may affect system performance and patient results.

Absorptiometry, Photon↗
PubMed1995

Ventilation and perfusion lung imaging--which nebulizer?

Three commercially available 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA) aerosol delivery nebulizers for lung ventilation imaging were investigated. Two were air-jet systems, 'Optimist' (Medicaid) and 'Microcirrus' (Amersham), and one was an ultrasonic device (Europlus). Altogether, 112 consecutive patients were scanned, 37 using the Optimist, 40 using the Microcirrus and 35 the Europlus. The age mix, FEV1, FVC and PEFR measurements of the patients in each group were similar. Each contained a proportion of patients with poor respiratory function, with PEFR rates ranging from 30 to 582 l min-1 for patients studied with all systems. Ease of use, image quality and cost were evaluated as well as radioactive and microbiological contamination. The Optimist system gave the best combination of image quality and cost, and was associated with the lowest level of radioactive contamination. It also proved the most popular. Airborne contamination for all nebulizers was lower than previously reported and was largely dependent on patient compliance. With poorly compliant patients, the contamination levels are sufficient to warrant an extraction device. There was no evidence of bacterial contamination of the nebulizers or tubing on repeated use over 5 days.

Forced Expiratory Volume↗
PubMed1995

A survey of dual-energy X-ray absorptiometry (DEXA) normal reference ranges used within the UK and their effect on patient classification.

Differences between dual-energy X-ray absorptiometry (DEXA) normal ranges can lead to patients being characterized as osteoporotic using one range and normal using another. To investigate the diversity of normal ranges used within the UK, a survey of all DEXA sites was carried out with a 60.6% response rate. The effect of the different ranges was evaluated by translating each range to an equivalent range for a Norland XR-26 system and applying the ranges to stratify a representative sample of over 1000 patients into grades of bone density based on percentages of age-matched mean BMD, Z-scores and T-scores. The effect of femoral neck and P/A spine L2-L4 regions was considered both separately and jointly. Large differences between the normal ranges were apparent, which resulted in the classification of the number of patients with a Z-score of less than -2.0 varying by a factor of more than 20 for the femoral neck and more than 3 for the spine. The number of patients defined as osteoporotic by a T-score less than -2.5 varied from none to over one-third of patients for the hip and by a factor of almost 3 for the spine. The exclusion criteria used for construction of the normal ranges varied markedly with none constructed using population-based sampling. Smoothing of normal ranges was carried out by DEXA manufacturers, while local normal ranges made use of raw unprocessed data. There is reason to question the validity of such processing. We recommend the construction of a unified UK normal range applicable to all UK DEXA systems in order to harmonize patient management and care.

Absorptiometry, Photon↗
PubMed1995

Home reporting for the nuclear clinician?

The computer-based 'home office' is becoming a widely accepted mode of operation for modern businesses. It is implausible to believe that a nuclear medicine department can be covered permanently at a distance by a single physician, but it should be possible to provide cover for colleagues during sickness or at night or weekends. We have used a 486 PC with a high-resolution screen and software provided by LINK Medical Ltd to obtain images from hospital sites using a modem link to ADAC, Bartec and Nuclear Diagnostic SUN workstations. The data were transferred via standard telephone lines to the homes of two of the authors. During a trial period lasting several months, 60 lung scans, 20 bone scans, 1 gastrointestinal bleeding study, 4 leukocyte scans, 5 bone tomograms, 9 renograms, 6 myocardial perfusion tomograms and 2 gated cardiac studies were transferred. The system allowed transfer of a 128 x 128 eight-view lung scan to be completed in approximately 2 min. The program on the PC allowed alteration of individual image contrast, image rotation, cine display and a variety of colour scales to enhance image interpretation. A system to transfer chest X-rays has been developed and typical transfer times are approximately 3.5 min. Within the viewing protocol on the PC, a reporting window was available with the ability to fax the report directly to the hospital. The system allowed consultants who live at a distance from their nuclear medicine departments to provide cover and is now used as an integral part of our out-of-hours service. The system also allows cover of satellite units or to provide cover for junior staff at night or weekends.

Computer Communication Networks↗
PubMed1995

Effect of a spacer on pulmonary aerosol deposition from a jet nebuliser during mechanical ventilation.

BACKGROUND: Several factors have been identified which improve nebulised aerosol delivery in vitro. One of these is the addition of a spacer to the ventilator circuit which improves aerosol delivery from a jet nebuliser to a model lung by approximately 30%. The current study was designed to demonstrate whether similar improvements could be demonstrated in vivo. METHODS: Ten patients (seven men) were studied during mechanical ventilation (Siemens Servo 900C) after open heart surgery. Aerosol was delivered using a Siemens Servo 945 nebuliser system (high setting) driving a System 22 Acorn jet nebuliser (Medic-Aid) containing 3 ml technetium-99m labelled human serum albumin (99mTc-HSA (50 micrograms); activity in the first nebulisation, 90 MBq; in the second nebulisation, 185 MBq). Central and peripheral lung aerosol deposition and the time to complete deposition were measured using a gamma camera and compared when the nebuliser was connected to the inspiratory limb using a simple T-piece or a 600 ml spacer. RESULTS: The addition of the spacer increased total lung deposition (mean (SD) percentage initial nebuliser activity) from 2.2 (0.7)% to 3 (0.8)%. There was no difference in the time required to complete nebulisation (18.2 min v 18.3 min respectively for T-piece and spacer) or in the retention of activity in the nebuliser (46.2% v 47.1% respectively). CONCLUSIONS: The combination of a spacer with a jet nebuliser increased lung deposition by 36% in mechanically ventilated patients and is a simple way of increasing drug deposition or reducing the amount of an expensive drug required for nebulisation.

Aerosols↗
PubMed1995

Dual energy X-ray absorptiometry normal reference range use within the UK and the effect of different normal ranges on the assessment of bone density.

The number of different normal ranges used on dual energy X-ray absorptiometry (DEXA) machines in the United Kingdom was determined by means of a postal questionnaire. Both femoral neck and posteroanterior spine L2-L4 regions were considered. It was clear from this survey that a variety of normal ranges were in use for all manufacturers of DEXA systems. The effects of four normal ranges supplied by Norland for use within the UK on the stratification of over 1000 consecutive patients into different grades of bone mineral density (BMD) and Z-score were examined. The main outcomes measure the number of patients with BMD less than 80% of mean age-matched BMD and Z-score less than -1.5 over the femoral neck and spine for each normal range. The percentage of patients for each normal range with BMD less than 80% of mean for the femoral neck were 24.6%, 7.4%, 17.5% and 11.1% and for the spine 12.1%, 7.4%, 16.5% and 14.4%, respectively. For the femoral neck, 21.2%, 5.0%, 12.9% and 12.1% of patients had Z-scores of less than -1.5, for the spine this was 7.9%, 8.1%, 14.2% and 13.6% of patients. These differences between ranges are large enough to influence patient management--patients may be diagnosed as osteoporotic using one range and normal using another. The relationship between hip and spine measurements was also studied as some therapeutic agents do not affect BMD equally at all anatomical sites. The number of patients with a lower hip than spine BMD grade varied from 12.3% to 34.4%, and with a lower hip than spine Z-score from 14.0% to 43.4%. Choice of normal range thus has a critical effect on the categorization of osteoporotic patients using DEXA. The wide variety of normal ranges indicates that there are likely to be differences in patient management throughout the country. This will be an increasing problem due to the ability of NHS purchasers to switch contracts from one provider to another.

Absorptiometry, Photon↗
PubMed1995

99mTc DTPA transfer/permeability in patients with HIV disease.

Lung 99mTc DTPA transfer/permeability has been widely used to assess the integrity of the lung alveolar-capillary interface. The use in HIV positive patients to provide a rapid assessment of causes of breathlessness or fever is discussed in this overview. There is I believe a clear role for this technique in this group of patients. It is more sensitive than Gallium-67 scanning in defining lung disease and is capable of distinguishing between alveolitic processes and bacterial infections of Kaposi sarcomatous infiltration. The 99mTc DTPA transfer/permeability can also define the absence of lung involvement in those patients with a fever to allow more suitable investigation to proceed. The 99mTc DTPA transfer/permeability measurement is a rapid, easy method of evaluating patients with HIV disease. Depending on the clinicians philosophy it can be used as a basis to initiate treatment or at the very least point to the next necessary investigation.

Blood-Air Barrier↗
PubMed1994

The effect of varying type and volume of sedimenting agents on leukocyte harvesting and labelling in sickle cell patients.

Leukocyte labelling in patients with sickle cell anaemia has been reported as difficult if not impossible due to the slow erythrocyte sedimentation rate (ESR) in these patients. This study investigated standard sedimentation methods in patients with sickle cell disease (n = 16) and compared the results obtained with those following changes in the amount and type of sedimenting agent used. Labelling with either 111In-oxine or 99Tcm-exametazime was attempted in only five patients. Replacement of the commonly used 6% Hetastarch (Hespan) with Dextran or Haemaccel did not improve leukocyte harvesting, even when the proportions used of these agents were increased. In most cases where standard procedures for leukocyte collection did not lead to harvesting of viable samples, it was possible to obtain adequate leukocyte labelling in the majority of sickle cell patients using a minor modification of standard techniques. In this group of patients a ratio of 8 ml of Hespan to 16 ml of blood should be used for cell separation. If this fails then donor cells, anti-granulocyte antibody labelling or HIG should be considered.

Anemia, Sickle Cell↗
PubMed1994

Effect of splenectomy on HIV-related thrombocytopenia and progression of HIV infection in patients with severe haemophilia.

Between May 1983 and September 1991 eleven patients with severe haemophilia underwent splenectomy for HIV-related thrombocytopenia. The sustained complete remission rate (platelets > 100 x 10(9)/l) was 82% over a mean follow-up period of 54 months. The group was compared with 22 age-matched non-thrombocytopenic HIV seropositive haemophiliacs who had not undergone splenectomy. Both groups had equivalent use of factor concentrate and there was no significant difference between the groups in terms of anti-retroviral treatment. Analysis of clinical progression of HIV infection and CD4 positive lymphocyte (CD4+) counts, for the time since splenectomy, revealed no significant difference in progression of HIV infection in the splenectomized group compared with the control group. It is concluded that splenectomy is an effective treatment for HIV-related thrombocytopenia and has no adverse effect on the progression of HIV infection.

CD4-Positive T-Lymphocytes↗
PubMed1994

Gastric emptying in patients with chronic renal failure on continuous ambulatory peritoneal dialysis.

Radionuclide gastric emptying studies were carried out on 20 patients with end-stage renal failure (ESRF) undergoing continuous ambulatory peritoneal dialysis (CAPD). Nine of the patients had diabetes mellitus. Eight normal volunteers were also studied to establish normal ranges. Solid and liquid emptying patterns were investigated simultaneously using a meal made up of a solid phase labelled with 99mTechnetium and a liquid phase labelled with 111Indium. The solid emptying fitted a model with a lag phase followed by a linear emptying phase and the liquid emptying fitted a single exponential. Nine of the 20 patients (four diabetic, five non-diabetic) were found to have delayed solid emptying, and four of these (two diabetic, two non-diabetic) also had delayed liquid emptying. No correlation was found between any of the parameters studied and the clinical symptoms of the patients. It is concluded that almost half of the patients studied had abnormal gastric emptying, but that many of these did not suffer from severe symptoms.

Diabetic Nephropathies↗