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Chemical pathology: what has changed?
  1. M A Crook1
  1. 1Department of Chemical Pathology, Guy's and St Thomas' Hospital, London SE1, UK

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    Is there really anything new under the sun?1 I wondered, as I was asked to select a chemical pathology paper from the first volume of the first edition of JCP, to discuss in the millennium issue of the journal. Furthermore, would it be possible for me to find a paper from over 50 years ago that would reflect chemical pathology practice at the time and contrast this with current trends in the field as we lead up to the millennium celebrations? A paper that did stand out was that by E J King and R J Garner, from the British Postgraduate Medical School, entitled “The colorimetric determination of glucose.”2 This was starkly different from those current papers that one tends to browse through, describing knock out mice, prions, cytokines, retroviruses, genetically modified foodstuffs, or adhesion molecules. It was written in 1947 during the preconception years of the NHS, at a time when laboratory accreditation, the Royal College of Pathology, CME log books, and NEQAS were only twinkles in laboratory medicine's eyes.

    The first striking feature of this paper is the mention in the introduction of the difficulty the authors had in obtaining analytic reagent grade quality reagents for the glucose colorimetric assay; they attributed this to the war years. Alas, in this sense perhaps little has changed, for as I write this article British forces attack Serbian positions in the Balkans, a tragic example of a “…small war on the heels of small war.”3 The contamination of their sodium carbonate reagent with sodium bicarbonate resulted in poor colour stability and variable glucose assay results. Today we perhaps take for granted the ease of obtaining high quality reagents off the shelf from large commercial suppliers.

    Another feature of this paper is the politically incorrect use of non-SI units. This is almost guaranteed to cause enthusiasts from the pro-SI and anti-SI lobbies to write letters to the Journal to generate debate, although I have to say that mmol/1 is a lot easier to write than mg per 100 ml for the units of glucose. Nevertheless, there is still no international agreement on units for reporting clinical chemistry results.

    As anyone should know who works in a modern chemical pathology laboratory, fast turnaround times are important for clinicians to ensure optimal patient management. However, I cannot imagine that manually filtering blood, after protein precipitation, followed by 10 minutes of boiling the filtrate with copper reagent, followed by another 10 minutes for assay colour development with Folin-Wu phosphomolybdic acid would inspire an overstretched MLSO to assay many blood samples for glucose. Nor would the beer barrel quantities of sample and reagent attract delight in a multidiscipline combined laboratory working flat out in a shift system; amazingly, the final assay reaction volume exceeded 5 ml! I would be surprised, also, if the authors of this historic paper would have guessed that 50 years later glucose could be measured within minutes, using microvolumes of sample and reagent by dry chemistry techniques, biosensors, or multianalysers, some of which can also measure at least 20 other analytes.

    Furthermore, would they have prophesied that diabetic patients would be monitoring their own blood glucose as part of near patient testing and using these results to adjust their insulin? In addition, could they have believed that in 1995 more than £40 million would be spent in the United Kingdom on home glucose monitoring alone!4

    Having read this fascinating, seminal, and historic paper by King and Garner I can only conclude that we have come a long way in laboratory medicine since they published their article. With the exponential growth in scientific and medical knowledge we are likely to have many further surprises in the new millennium. Fifty years is a long time in laboratory medicine and we need to be prepared for the changes if we are to survive under the sun.

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