title: Correlation Between Capillary and Venous Blood Glucose in the Lactose Tolerance Test.
abstract: BACKGROUND
  The lactose tolerance test is a classic method for the study of lactose malabsorption. However, the methodology used has not been standardized, and this leads to differences in results.
  
  
  OBJECTIVE
  The aim of this report was to analyze whether capillary blood glucose measurement is in agreement with venous blood glucose when performing lactose tolerance test.
  
  
  METHODS
  This is a prospective study of consecutive patients with suspected lactose malabsorption who had lactose tolerance test performed in venous and capillary blood simultaneously, using a load of 50 g lactose. Agreement was measured using the concordance correlation coefficient of Lin (95 % CI) and Bland-Altman plots. The degree of agreement was measured using the Kappa index. A value of p < 0.05 was considered statistically significant.
  
  
  RESULTS
  Eighty-four patients (68 % women) were included. The concordance correlation coefficient showed very poor agreement between the two techniques: 0.68 (0.58-0.77), 0.72 (0.62-0.8), and 0.77 (0.69-0.83) for baseline, 30, and 60 min, respectively. The Bland-Altman plots showed that capillary blood glucose measurements result in higher levels than venous blood glucose measurements, with mean differences of 0.39, 0.77, and 1.1 mmol/L at baseline, 30, and 60 min, respectively. The degree of agreement was low, with a Kappa index of 0.59 (p < 0.001).
  
  
  CONCLUSIONS
  The test measured in venous blood is not in agreement with the measurement obtained from capillary blood. It is likely that the diagnostic accuracy attributed without distinction to lactose tolerance test in different studies for lactose malabsorption is incorrect, making it necessary to specify the analysis method.
authors: Department of Gastroenterology and Hepatology, Alto Guadalquivir Healthcare Agency, Alto Guadalquivir Hospital, Blas Infante Ave, Andújar, Jaén, 23740, Spain. jldominguezjim@hotmail.com.
authors: José Luis
authors: JL
authors: Domínguez Jiménez
authors: Department of Biotechnology, Alto Guadalquivir Healthcare Agency, Alto Guadalquivir Hospital, Andújar, Jaén, Spain.
authors: Antonio
authors: A
authors: Fernández Suárez
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism*; D002196:Capillaries; D005260:Female; D005385:Fingers / Q000098:blood supply; D006801:Humans; D007787:Lactose Intolerance / Q000097:blood / Q000175:diagnosis*; D007789:Lactose Tolerance Test / Q000295:instrumentation / Q000379:methods*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011934:Reagent Strips; D015203:Reproducibility of Results; D034941:Upper Extremity / Q000098:blood supply*; D014680:Veins
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D011934:Reagent Strips
keywords: Glycemic variability; Lactose intolerance diagnosis; Lactose malabsorption; Lactose tolerance test