- Email: [email protected]
Home blood-glucose monitoring
CORRESPONDENCE
Home blood-glucose monitoring Sir-On account of their experimental data, M Urdang and colleagues (March 27, p 1065)' conclude that a reliable test solution is needed for the quality assessment of a wide range of home blood-glucose monitors. We agree that present quality controls are inadequate, but would like to comment on the study design and the interpretation. Most home blood-glucose monitors are designed and validated for capillary whole blood only. The use of other glucose-containing materials (eg, plasma, arterial blood, venous blood, or Sugar-Chex) produces values that may differ from the actual glucose on cent ration.^^' These differences are related to complex and system-specific interactions between substrate and test strip.3 Therefore, conversion factors between the blood-glucose monitor and the laboratory reference method should be calculated for every type of solution and monitor. Without these conversion factors, the accuracy of a glucose monitor can only be assessed with the material for which it was validated, which in most cases is capillary whole blood. Therefore, rather than reliable test solutions, system-specific conversion factors for (standard) glucose solutions are needed. These factors should be provided and updated by the manufacturers of glucose monitors, since only they are informed on relevant changes in test-strip design of differences between production runs. Roche Diagnostics (manufacturer of five of the test instruments),' does not provide these factors for Sugar-Chex (personal communication). Theoretically, Sugar-Chex should not therefore be used for quality controls with these instruments, irrespective of its reliability as a stable glucose solution and the reference ranges provided. As an alternative to commercial test solutions, all home blood-glucose monitors can be easily tested with capillary blood samples.4 Paired measurements with a glucose monitor and a standardised laboratory method adequately reflect the accuracy of the device in its proper use. These quality controls could be done during visits to the outpatient clinic or during hospital admissions. Results should be kept to assess changes in accuracy of the monitor-test-strip combination over time. Capillary whole blood is the proper test solution for all home blood-
252
glucose monitors. The reliability of other glucose solutions depends on accurate and instrument-specific conversion factors provided by glucose-monitor manufacturers. * W Brinkert, J Bakker Department of Intensive Care, ZC Lukas Hospital, 7300 DS Apeldoorn, Netherlands (e-mail: [email protected])
Urdang M, Ansede-Luna G, Muller B, Newson R, Lacy-Petit A, O'Shea D. An independent pilot study into the accuracy and reliability of home blood glucose monitors. Lancet 1999; 353: 1065-66. Maser RE, Butler MA, DeCherney GS. Use of arterial blood with bedside glucose reflectance meters in an intensive care unit: are they accurate? C ~Cave t Med 1994; 22: 595-99. Wiener I<. Whole blood glucose: what are we actually measuring? Ann Clin Biochem 1995; 32: 1-8. Johnson RN, Baker JR. Accuracy of devices used for self-monitoring of blood glucose. Ann Clin Biochem 1998; 35: 68-74.
Authors' reply Sir-We
thank W Brinkert
and
J Bakker for their comments, and for agreeing that there are no reliable independent quality control solutions available for checking the accuracy of home blood-glucose monitors. They suggest glucose solutions provided by the monitor manufacturer as one alternative. We agree that these solutions are an important component of regular internal quality control, but they cannot be regarded as an independent assessment. Manufacturers' views on producing system-specific conversion factors for a universal testing solution with a facility for a regular update would be intriguing. The alternative of parallel testing with a laboratory method on paired capillary samples brings its own organisational and method-related difficulties. Blood for laboratory analysis must either be analysed immediately (or, at least, centrifuged, snap frozen, or protein precipitated), to avoid glucose losses, which occur even in fluoride oxalate containers.' We believe that the increasing number of available monitors requires that a simple means for independent quality assessment should continue to be sought. * M Urdang, B Muller, D O'Shea Imperial College School of Medicine, Charing Cross Campus, London W 6 8FR. UK (e-mail: [email protected])
1 de Pasqua A, Mattock MB, Phillips R, Keen H. Errors in blood glucose determination. L a r u t 1984; ii: 1165.
High-dose chemotherapy for breast cancer in USA Sir-We were disappointed that your May 15 editorial' criticised the American Society of Clinical Oncology (ASCO) for the early release of research on high-dose chemotherapy in breast cancer. Had you spoken with ASCO before publishing the piece you would have been able to provide your readers with a more accurate account of ASCO's decision to break with tradition and release the preliminary results early. The decision was reached after months of deliberation, and was a community decision-agreed upon by ASCO, the National Cancer Institute, the investigators themselves, and leaders in the US breast cancer advocacy community. The decision was made for one primary reason: to ensure that the information was portrayed responsibly and accurately. Intense public interest in the results, the imminent distribution of ASCO's abstract book to members, and inaccurate news accounts in early April weighed heavily in our decision. Major US news organisations were already reporting incomplete and misleading stories. Had we waited until the Annual Meeting, it was all but guaranteed that additional news would be leaked piecemeal, and that the overall findings would be reported irresponsibly. We did what, in a far from ideal situation, we believed was the most responsible thing to do-to release preliminary information on research that the public was eager to know, with responsible context and background information. ASCO, along with the National Cancer Institute, the investigators, and leading breast-cancer organisations, also took great pains to indicate that the data were preliminary, that this research would not in any way be the final word on high-dose chemotherapy in breast cancer, and that much additional study would be needed-statements borne out by the debate that ensued at the Annual Meeting itself. There is little question that the medical field in the USA has entered a new era, especially with regard to embargo policies.2 Providing medical information to the public as quickly as possible has become of paramount importance. Cases in point: the National Cancer Institute recently released the early results of five studies on cervical cancer before publication; even J A M , the New England Journal of Medicine, and the Journal of Clinical Oncology now publish early-release papers, before the actual issue is sent to subscribers.
THE LANCET * Vol354 *July 17, 1999
Home blood-glucose monitoring Sir-On account of their experimental data, M Urdang and colleagues (March 27, p 1065)' conclude that a reliable test solution is needed for the quality assessment of a wide range of home blood-glucose monitors. We agree that present quality controls are inadequate, but would like to comment on the study design and the interpretation. Most home blood-glucose monitors are designed and validated for capillary whole blood only. The use of other glucose-containing materials (eg, plasma, arterial blood, venous blood, or Sugar-Chex) produces values that may differ from the actual glucose on cent ration.^^' These differences are related to complex and system-specific interactions between substrate and test strip.3 Therefore, conversion factors between the blood-glucose monitor and the laboratory reference method should be calculated for every type of solution and monitor. Without these conversion factors, the accuracy of a glucose monitor can only be assessed with the material for which it was validated, which in most cases is capillary whole blood. Therefore, rather than reliable test solutions, system-specific conversion factors for (standard) glucose solutions are needed. These factors should be provided and updated by the manufacturers of glucose monitors, since only they are informed on relevant changes in test-strip design of differences between production runs. Roche Diagnostics (manufacturer of five of the test instruments),' does not provide these factors for Sugar-Chex (personal communication). Theoretically, Sugar-Chex should not therefore be used for quality controls with these instruments, irrespective of its reliability as a stable glucose solution and the reference ranges provided. As an alternative to commercial test solutions, all home blood-glucose monitors can be easily tested with capillary blood samples.4 Paired measurements with a glucose monitor and a standardised laboratory method adequately reflect the accuracy of the device in its proper use. These quality controls could be done during visits to the outpatient clinic or during hospital admissions. Results should be kept to assess changes in accuracy of the monitor-test-strip combination over time. Capillary whole blood is the proper test solution for all home blood-
252
glucose monitors. The reliability of other glucose solutions depends on accurate and instrument-specific conversion factors provided by glucose-monitor manufacturers. * W Brinkert, J Bakker Department of Intensive Care, ZC Lukas Hospital, 7300 DS Apeldoorn, Netherlands (e-mail: [email protected])
Urdang M, Ansede-Luna G, Muller B, Newson R, Lacy-Petit A, O'Shea D. An independent pilot study into the accuracy and reliability of home blood glucose monitors. Lancet 1999; 353: 1065-66. Maser RE, Butler MA, DeCherney GS. Use of arterial blood with bedside glucose reflectance meters in an intensive care unit: are they accurate? C ~Cave t Med 1994; 22: 595-99. Wiener I<. Whole blood glucose: what are we actually measuring? Ann Clin Biochem 1995; 32: 1-8. Johnson RN, Baker JR. Accuracy of devices used for self-monitoring of blood glucose. Ann Clin Biochem 1998; 35: 68-74.
Authors' reply Sir-We
thank W Brinkert
and
J Bakker for their comments, and for agreeing that there are no reliable independent quality control solutions available for checking the accuracy of home blood-glucose monitors. They suggest glucose solutions provided by the monitor manufacturer as one alternative. We agree that these solutions are an important component of regular internal quality control, but they cannot be regarded as an independent assessment. Manufacturers' views on producing system-specific conversion factors for a universal testing solution with a facility for a regular update would be intriguing. The alternative of parallel testing with a laboratory method on paired capillary samples brings its own organisational and method-related difficulties. Blood for laboratory analysis must either be analysed immediately (or, at least, centrifuged, snap frozen, or protein precipitated), to avoid glucose losses, which occur even in fluoride oxalate containers.' We believe that the increasing number of available monitors requires that a simple means for independent quality assessment should continue to be sought. * M Urdang, B Muller, D O'Shea Imperial College School of Medicine, Charing Cross Campus, London W 6 8FR. UK (e-mail: [email protected])
1 de Pasqua A, Mattock MB, Phillips R, Keen H. Errors in blood glucose determination. L a r u t 1984; ii: 1165.
High-dose chemotherapy for breast cancer in USA Sir-We were disappointed that your May 15 editorial' criticised the American Society of Clinical Oncology (ASCO) for the early release of research on high-dose chemotherapy in breast cancer. Had you spoken with ASCO before publishing the piece you would have been able to provide your readers with a more accurate account of ASCO's decision to break with tradition and release the preliminary results early. The decision was reached after months of deliberation, and was a community decision-agreed upon by ASCO, the National Cancer Institute, the investigators themselves, and leaders in the US breast cancer advocacy community. The decision was made for one primary reason: to ensure that the information was portrayed responsibly and accurately. Intense public interest in the results, the imminent distribution of ASCO's abstract book to members, and inaccurate news accounts in early April weighed heavily in our decision. Major US news organisations were already reporting incomplete and misleading stories. Had we waited until the Annual Meeting, it was all but guaranteed that additional news would be leaked piecemeal, and that the overall findings would be reported irresponsibly. We did what, in a far from ideal situation, we believed was the most responsible thing to do-to release preliminary information on research that the public was eager to know, with responsible context and background information. ASCO, along with the National Cancer Institute, the investigators, and leading breast-cancer organisations, also took great pains to indicate that the data were preliminary, that this research would not in any way be the final word on high-dose chemotherapy in breast cancer, and that much additional study would be needed-statements borne out by the debate that ensued at the Annual Meeting itself. There is little question that the medical field in the USA has entered a new era, especially with regard to embargo policies.2 Providing medical information to the public as quickly as possible has become of paramount importance. Cases in point: the National Cancer Institute recently released the early results of five studies on cervical cancer before publication; even J A M , the New England Journal of Medicine, and the Journal of Clinical Oncology now publish early-release papers, before the actual issue is sent to subscribers.
THE LANCET * Vol354 *July 17, 1999