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Labtracker+, a medical smartphone app for the interpretation of consecutive laboratory results: an external validation study
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    Time-dependency of within-subject biological variation
    • George S Cembrowski, Clinical Pathologist Laboratory Medicine and Pathology, University of Alberta

    The authors state that least 21 of the 106 analytes exhibited time dependent increases in biological variation. Such increases can be due to at least two different factors: 1) seasonal variation if more than 2 or 3 months elapse between sequential tests in a subject living in a non-equatorial region and 2) diurnal variation with sequential intra-subject measurements occurring within a day in analytes that exhibit large diurnal variation. In fact, many of the authors of the Labtracer+ validation recently published a remarkable paper documenting large intra-day, intra-subject variation in components of the complete blood count (Reference). What are the 21 analytes that exhibit increased biological variation and would the authors provide the literature citations documenting these variations?

    Hilderink JM, Klinkenberg LJ, Aakre KM, de Wit NC, Henskens YM, van der Linden N, Bekers O, Rennenberg RJ, Koopmans RP, Meex SJ. Within-day biological variation and hour-to-hour reference change values for hematological parameters. Clinical Chemistry and Laboratory Medicine (CCLM). 2017 Jun 27;55(7):1013-24.

    Conflict of Interest:
    None declared.