- Email: [email protected]
Ultrasound equipment evaluation project
437
CLINICAL RADIOLOGY presence of pelvic arterial calcification is important to know prior to renal transplantation but does not require annual monitoring. Nonvascular soft tissue calcification is troublesome when symptomatic or prominent. But here again it is unusual to have radiographically identifiable soft tissue calcification with a Ca x P product of less than 75 rag%. The decision to continue skeletal surveys on an arbitrarily determined 12 m o n t h interval does not fit the observations these authors have made in their thorough study except maybe for purposes of research. It would seem to us far more cost effective to limit skeletal surveys to a baseline examination and obtain further radiographs for unexplained symptoms and/or unexplained biochemical alterations. M. S U N D A R A M P. F. JOYCE
N. C H A L M E R S
Department of Radiology St Louis University Medical Centre Missouri 63104, USA
SIR We have recommended annual skeletal surveys for research purposes, but also to complement the biochemical changes. Although bone biopsy is the gold standard for assessment of osteitis fibrosa as a measure of the skeletal effects of secondary hyperparathyroidism, it is invasive, uncomfortable, associated with some morbidity, requires expert histopathological interpretation and is not routinely available to a substantial number of renal units. In our experience clinical symptoms are a late manifestation of secondary hyperparathyroidism and modern nephrological practice is to try and prevent the development of skeletal manifestations rather than waiting until the patient becomes symptomatic. Whilst serum biochemistry is a good guide to progressing secondary hyperparathyroidism, there are problems in interpretation of alkaline phosphatase estimations without access to alkaline phosphatase isoenzyme measurement, unless the serum alkaline phosphatase is raised more than two or three times the normal value and the patient is known not to have any evidence of liver disease. We agree that vascular calcification is usually irreversible but its appearance and progression does influence management, since it leads to an increased motivation to lower plasma phosphate when high and to lower elevated plasma calcium if necessary by earlier recourse to parathyroidectomy. Whilst we would still advocate yearly skeletal surveys in patients on haemodialysis and peritoneal dialysis we have recently decided to radiograph our transplant patients every three years because of their low rate of positive radiological findings. J. P. O W E N M. K. W A R D R. W I L K I N S O N
If the conclusions of the article are to be sustained then the column headings 'False Negative' and 'False Positive' should be reversed, the number of False Negatives for the Enlarged Pyramids sign changed from 20 to 30, and that for the Increased Volume sign changed from 10 to 9. This would give a total of 43 patients in the true positive plus false negative groups for each sign, and would correct the numerical errors. This is equal to the number of patients in the authors' 'Intermediate Group'. I assume these are printing errors. Unfortunately they detract from an otherwise interesting article.
Department of Radiology The Royal Victoria Infirmary Queen Victoria Road Newcastle Upon Tyne NE1 4LP
SIR In reply to Dr N. Chalmer's letter, the headings 'False Negative' and 'False Positive' in Table 1 are indeed reversed, and I thank Dr Chalmers for drawing attention to this, and apologise for allowing this error to occur. The other figures are correct; 'Sensitivity' being calculated against all scans, not just true positives. D. LL. C O C H L I N
SiR As you may know, the Ultrasonic Equipment Evaluation Project (UEEP) has been assessing ultrasonic scanners since 1985. This project is funded by the Chief Scientist Office, Scottish H o m e and Health Department through a C o m m o n Services Agency Advisory Panel and is carried out with the collaboration of the Department of Health. The aim of the project is to provide purchasers of ultrasonic equipment with comparative performance data on which to base their choice of equipment. This information is published in the Department of Health 'Blue Cover' series of reports which are available free of charge to N H S personnel. These reports include the assessment of safety, reliability and both clinical and technical performance and are produced in a standard format to allow meaningful comparisons to be made. Evaluation Reports on 13 scanners have been published to date with new reports appearing at a rate of four to five per annum. One special additional feature of the current programme is the comparative evaluation of a range of ultrasonic scanners suitable for use in Breast Screening Clinics. The report on this exercise should be published later in the year. Copies of reports or further information may be obtained by contacting me at the address below (Tel. 031 552 6255 ext. 2077). -
U L T R A S O U N D C H A N G E S IN T H E T R A N S P L A N T KIDNEY
(true pos/(true pos + false pos)) x 100 in the table as shown. If this is the case then there are numerical errors in two rows of the table.
Department of Radiology Cardiff Royal Infirmary Newport Road, Cardiff CF2 1SZ
ULTRASOUND EQUIPMENT EVALUATION PROJECT
A. W A T T
SIR The data presented by Cochlin et al. (1988), in Table 1 of their article on 'Ultrasound Changes in the Transplant Kidney' are inaccurate. In the table, either the column headings 'False Negative' and 'False Positive' are the wrong way round, or else 'Sensitivity' and 'Specificity' are incorrect. Also, assuming all four signs of rejection were looked for in every case, then the total number of 'True Positives' and 'False Negatives' should be the same for each sign. This is not the case either with the columns as shown or with 'False Negative' and 'False Positive' reversed. Finally, the figures for 'Sensitivity %' appear to have been calculated from the formula
Department of Radiology Western General Hospital Crewe Road, Edinburgh
Evaluation Officer Trinity Park House South Trinity Road Edinburgh EH5 3SH
Erratum Low Dose Low Osmolar Intravenous Urography. Clinical Radiology, 40, 325. We apologise for an error in the letter by Drs Eyes and Goldman. 'Low Dose Osmolar Intravenous Urography' should have read 'Low Dose Low Osmolar Intravenous Urography'.
CLINICAL RADIOLOGY presence of pelvic arterial calcification is important to know prior to renal transplantation but does not require annual monitoring. Nonvascular soft tissue calcification is troublesome when symptomatic or prominent. But here again it is unusual to have radiographically identifiable soft tissue calcification with a Ca x P product of less than 75 rag%. The decision to continue skeletal surveys on an arbitrarily determined 12 m o n t h interval does not fit the observations these authors have made in their thorough study except maybe for purposes of research. It would seem to us far more cost effective to limit skeletal surveys to a baseline examination and obtain further radiographs for unexplained symptoms and/or unexplained biochemical alterations. M. S U N D A R A M P. F. JOYCE
N. C H A L M E R S
Department of Radiology St Louis University Medical Centre Missouri 63104, USA
SIR We have recommended annual skeletal surveys for research purposes, but also to complement the biochemical changes. Although bone biopsy is the gold standard for assessment of osteitis fibrosa as a measure of the skeletal effects of secondary hyperparathyroidism, it is invasive, uncomfortable, associated with some morbidity, requires expert histopathological interpretation and is not routinely available to a substantial number of renal units. In our experience clinical symptoms are a late manifestation of secondary hyperparathyroidism and modern nephrological practice is to try and prevent the development of skeletal manifestations rather than waiting until the patient becomes symptomatic. Whilst serum biochemistry is a good guide to progressing secondary hyperparathyroidism, there are problems in interpretation of alkaline phosphatase estimations without access to alkaline phosphatase isoenzyme measurement, unless the serum alkaline phosphatase is raised more than two or three times the normal value and the patient is known not to have any evidence of liver disease. We agree that vascular calcification is usually irreversible but its appearance and progression does influence management, since it leads to an increased motivation to lower plasma phosphate when high and to lower elevated plasma calcium if necessary by earlier recourse to parathyroidectomy. Whilst we would still advocate yearly skeletal surveys in patients on haemodialysis and peritoneal dialysis we have recently decided to radiograph our transplant patients every three years because of their low rate of positive radiological findings. J. P. O W E N M. K. W A R D R. W I L K I N S O N
If the conclusions of the article are to be sustained then the column headings 'False Negative' and 'False Positive' should be reversed, the number of False Negatives for the Enlarged Pyramids sign changed from 20 to 30, and that for the Increased Volume sign changed from 10 to 9. This would give a total of 43 patients in the true positive plus false negative groups for each sign, and would correct the numerical errors. This is equal to the number of patients in the authors' 'Intermediate Group'. I assume these are printing errors. Unfortunately they detract from an otherwise interesting article.
Department of Radiology The Royal Victoria Infirmary Queen Victoria Road Newcastle Upon Tyne NE1 4LP
SIR In reply to Dr N. Chalmer's letter, the headings 'False Negative' and 'False Positive' in Table 1 are indeed reversed, and I thank Dr Chalmers for drawing attention to this, and apologise for allowing this error to occur. The other figures are correct; 'Sensitivity' being calculated against all scans, not just true positives. D. LL. C O C H L I N
SiR As you may know, the Ultrasonic Equipment Evaluation Project (UEEP) has been assessing ultrasonic scanners since 1985. This project is funded by the Chief Scientist Office, Scottish H o m e and Health Department through a C o m m o n Services Agency Advisory Panel and is carried out with the collaboration of the Department of Health. The aim of the project is to provide purchasers of ultrasonic equipment with comparative performance data on which to base their choice of equipment. This information is published in the Department of Health 'Blue Cover' series of reports which are available free of charge to N H S personnel. These reports include the assessment of safety, reliability and both clinical and technical performance and are produced in a standard format to allow meaningful comparisons to be made. Evaluation Reports on 13 scanners have been published to date with new reports appearing at a rate of four to five per annum. One special additional feature of the current programme is the comparative evaluation of a range of ultrasonic scanners suitable for use in Breast Screening Clinics. The report on this exercise should be published later in the year. Copies of reports or further information may be obtained by contacting me at the address below (Tel. 031 552 6255 ext. 2077). -
U L T R A S O U N D C H A N G E S IN T H E T R A N S P L A N T KIDNEY
(true pos/(true pos + false pos)) x 100 in the table as shown. If this is the case then there are numerical errors in two rows of the table.
Department of Radiology Cardiff Royal Infirmary Newport Road, Cardiff CF2 1SZ
ULTRASOUND EQUIPMENT EVALUATION PROJECT
A. W A T T
SIR The data presented by Cochlin et al. (1988), in Table 1 of their article on 'Ultrasound Changes in the Transplant Kidney' are inaccurate. In the table, either the column headings 'False Negative' and 'False Positive' are the wrong way round, or else 'Sensitivity' and 'Specificity' are incorrect. Also, assuming all four signs of rejection were looked for in every case, then the total number of 'True Positives' and 'False Negatives' should be the same for each sign. This is not the case either with the columns as shown or with 'False Negative' and 'False Positive' reversed. Finally, the figures for 'Sensitivity %' appear to have been calculated from the formula
Department of Radiology Western General Hospital Crewe Road, Edinburgh
Evaluation Officer Trinity Park House South Trinity Road Edinburgh EH5 3SH
Erratum Low Dose Low Osmolar Intravenous Urography. Clinical Radiology, 40, 325. We apologise for an error in the letter by Drs Eyes and Goldman. 'Low Dose Osmolar Intravenous Urography' should have read 'Low Dose Low Osmolar Intravenous Urography'.