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  1. Response to e-letter

    We sincerely thank the technical product manager of ACCU-CHEK Performa (Roche) for going through our article entitled 'Erroneously elevated glucose values due to maltose interference in mutant GDH-PQQ based glucometer, Chakraborty PP, et al. BMJ Case Rep 2017. doi:10.1136/bcr-2017-219928 with interest. We provide our response to the issues raised by our learned colleague.

    Regarding the removal of maltose-containing infusion tube from the intravenous cannula by the patient himself; yes, it is unacceptable but probably not that uncommon in real life. It is possible for an extremely agitated patient experiencing respiratory distress to remove the IV line himself if left unattended for fraction of a second without waiting for medically trained staffs to do their jobs. They have also expressed their concerns regarding measurement of capillary glucose from an uncleaned hand. In an intensive care setting, it may not be possible to "wash the hands in warm, soapy water. Rinse and dry completely" before checking capillary blood glucose in a patient who is actively seizing or having altered sensorium as instructed in the package insert of ACCU-CHEK Performa.

    The package insert of ACCU-CHEK Performa categorically mentions about the elevated levels of galactose (>15mg/dl or >0.83 mmol/L), triglycerides (>1,800mg/dl or >20.3 mmol/L) , ascorbic acid (>3mg/dl or >0.17mmol/L), haematocrit (should be between 10-65%) that may cause erroneous glucose values. It has pointed towards "clinically relevant maltose interference" without mentioning the concentration of maltose known to be associated with such interference.

    This e-letter has discussed issues, which had already been focused in our article. The probable reasons of erroneous capillary glucose values, the difference of capillary glucose values between right and left hand fingertips, the blood level of maltose which is unlikely to cause such interference have already been highlighted in our article.

    Sir, what we have discussed in our article is exactly what we had experienced in our clinical ward rounds. We strongly believe proper protocol has to be followed in each and every step and this article is definitely a "reminder of important clinical lesson" of violating the basic principles. We do not have the intention to spread false information related to any manufacturing company & we do not endorse such ideas ever. Having said that, we strongly believe that the package insert of ACCU-CHEK Performa should specify the maltose concentration that may cause overestimation of blood glucose.

    Conflict of Interest:

    None declared

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  2. The importance of proper hygiene in self-monitoring of blood glucose

    Authors: Sami Wardat, PhD, MBA(1), Oliver Hauss, PhD(2), and Rolf Hinzmann, MD, PhD(1)

    Dear Editor,

    Partha Pratim Chakraborty and Shinjan Patra recently reported on a potential risk for patients welfare from maltose interference with glucose measurements in their case report Erroneously elevated glucose values due to maltose interference in mutant GDH-PQQ based glucometer, Chakraborty PP, et al. BMJ Case Rep 2017. doi:10.1136/bcr-2017-219928.

    The authors are concerned that patients on maltose-containing therapies may receive an excessive dose of insulin due to falsely elevated blood glucose readings, leading to a hypoglycemic episode, and that, likewise, cases of hypoglycemia might not be treated if patients hypoglycemic states are masked by false blood glucose measurements.

    Our review of this case reports circumstances indicates that the situation described is highly unusual and based on violation of proper protocol on multiple levels.

    As for the course of events, the patient removed a maltose-containing infusion tube from the intravenous cannula himself. This is clearly not in line with the standards of medical practice and carries itself a significant risk to the patients safety. The removal of intravenous (i.v.) tubes should be left to properly trained medical personnel to avoid injuries. The infusion solution subsequently contaminated the patients left hand and a glucose measurement was taken from that very hand, without it being cleaned first. Our instructions for performing a blood glucose test for consumers clearly instruct patients to wash and dry their hands prior to using the lancing device (See Accu-Chek Performa manual page 10 available for India at https://www.accu-chek.in/meter-systems/performa ). We instruct healthcare practitioners to follow their institutional policies and assume these would suggest comparable standards of contamination prevention.

    As a result of violating proper medical procedures on two levels, the glucose measurement device was exposed to 10% maltose solution, which contains 100 mg/mL maltose, i.e. 10 000 mg/dL = 100 g/L or 320 mmol/L. This is around 30 times higher than the maltose concentrations tested in the clinical evaluation report on Accu-Chek Performa (400 mg/dL or 11.7 mmol/L). Thus, the interference should not come as a surprise and is to be expected.

    The 100 mL of i.v. human immunoglobulin (IVIG) solution provided would have been administered in a short time frame of 15 to 30 min (based on the dosage indication for PlasmaGlob, which is 1.2 mL/kg of bodyweight, and on the assumption that the patient weighs around 80-85 kg). This would mean that roughly 200 mg/dL of maltose could be expected in the blood circulation, which would normally not result in interference with the mutant GDH-PQQ enzyme in the test strips.

    Furthermore, the situation is also not specific to maltose and the sensitivity to maltose interference of the enzyme used: if we assumed that the solution contained glucose, then the reading of any device, even one without sensitivity to maltose interference, would still show a false high concentration due to the undiluted solution present on the hands, thus preventing accurate measurement of the concentration within the circulating blood.

    The 50% difference between the heavily contaminated left hand and the right hand, which was likely only cross-contaminated, indeed points to external contamination as the key factor in the observation.

    The failure to heed the instructions concerning basic hand washing can hardly be seen as a significant risk posed by the product itself. It should be clear that blood should only be drawn from clean hands to prevent cases of cross-contamination.

    Therefore, we do not mandate any further steps other than strongly appealing to both patients and medical personnel to abide by our instructions to wash their hands before obtaining capillary blood and by general protocol, which would have been sufficient to prevent this course of events.

    Affiliations:

    1.
    Roche Diabetes Care GmbH
    Global Medical & Scientific Affairs
    Sandhofer Strasse 116
    68305 Mannheim / Germany

    2.
    Dr. Hauss Training & Consulting
    Lorscher Str. 24
    67133 Maxdorf / Germany

    Conflict of Interest:

    Sami Wardat and Rolf Hinzmann are employees of Roche Diabetes Care GmbH. Oliver Hauss is an independent consultant contracted by Roche Diabetes Care GmbH

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