Valutazioni preliminari per la proposta di un unico dispositivo di campionamento per la ricerca dell’emoglobina su materiale fecale
1Laboratorio Generale, Dipartimento Servizi, Azienda Ospedaliero Universitaria Careggi, Firenze
2Center for Research in Cancer Prevention and Screening, University of Dundee Ninewells Hospital and Medical School, Dundee, Scotland
3Laboratorio Prevenzione Oncologica, Istituto Studio Prevenzione Oncologica, Firenze
Preliminary assessments for a standard sampling device for fecal hemoglobin detection
Sampling of feces is strongly affected by the lack of harmonisation, with differences up to 20 times in the mass collected for immunological tests for fecal hemoglobin (Hb) used in colorectal cancer screening. Aim of this study was to acquire information on fecal sampling and on the interaction between feces and analytical methods to obtain a reference design for a sampling dipstick. Bias and imprecision of sample collection dipsticks were estimated using gravimetry. Dissolution times of feces were monitored throughout the study. The effect of increasing amount of feces on Hb concentrations was investigated in saline and buffers of different manufacturers using a single analytical method (OC-Sensor, Eiken Chemical Co.). Fecal mass recovered with different devices ranged from 56 to 121% of declared amount (CV range: 8.6÷31.1%). Time of dissolution up to 2 h was observed when lumps of materials were collected. In saline a rapid decrease of Hb values was observed, which was related to the overall amount of feces. Increased Hb values were
observed by adding feces to manufacturers’ buffers. Solubilisation time, bias and imprecision of sampling of feces were related to device design. Analytical methods are designed to use specific ratios between feces and buffers. The introduction of a standard dipstick design to reduce preanalytical variability may represent a crucial step for fecal test harmonization.