Editing Glucose tolerance test (section)

==Sample method==
The diagnosis criteria stated above by the World Health Organization (WHO) are for venous samples only (a blood sample taken from a vein in the arm). An increasingly popular method for measuring blood glucose is to sample capillary or finger-prick blood, which is less invasive, more convenient for the patient and requires minimal training to conduct. Though fasting blood glucose levels have been shown to be similar in both capillary and venous samples, postprandial blood glucose levels (those measured after a meal) can vary.<ref name=nevander>{{cite journal | last1=Nevander | first1=Sofia | last2=Landberg | first2=Eva | last3=Blomberg | first3=Marie | last4=Ekman | first4=Bertil | last5=Lilliecreutz | first5=Caroline | title=Comparison of Venous and Capillary Sampling in Oral Glucose Testing for the Diagnosis of Gestational Diabetes Mellitus: A Diagnostic Accuracy Cross-Sectional Study Using Accu-Chek Inform II | journal=Diagnostics| volume=10 | issue=12 | date=26 November 2020 | issn=2075-4418 | doi=10.3390/diagnostics10121011|doi-access=free | page=1011| pmid=33255868 | pmc=7760160 }}</ref> The diagnosis criteria issued by the WHO are only suitable for venous blood samples. Given the increasing popularity of capillary testing, the WHO has recommended that a conversion factor between the two sample types be calculated, but {{As of|2017|lc=y}} no conversion factor had been issued by the WHO, despite some medical professionals adopting their own.{{citation needed|date=November 2021}} A 2020 study on pregnant women for gestational diabetes mellitus (GDM) found that 0-hour venous and capillary levels were similar, but that 2-hour samples were different. The authors compared their study with others, and concluded that capillary samples could be used for diagnosis of GDM during pregnancy using corrected cutoffs with acceptable accuracy in an antenatal care setting.<ref name=nevander/><!--older WHO documents find fairly consistently that capillary values are similar at 0h, and about 1.1mmol/l higher at 2 hours, reasonably consistent with Nevander et al. https://apps.who.int/iris/rest/bitstreams/51753/retrieve (1994). https://applications.emro.who.int/dsaf/dsa509.pdf (2006). This could be added to the article, but should perhaps be discussed first.-->