HAEMOGLOBIN CONCENTRATION IN FAECES FROM ONE TO 48 HOURS AFTER SAMPLING USING THREE FIT ANALYTICAL SYSTEMS


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Cerin John1,Carolyn Piggott1,Helen Bruce1
1NHS Bowel Cancer Screening Programme -Southern Hub

Abstract

Background

Automated quantitative faecal immunochemical tests (FIT) for haemoglobin (Hb) include a sampling device and an analytical system. In colorectal cancer screening, samples are usually collected at home and returned to the laboratory for testing. The manufacturers state one hour minimum before analysis to allow Hb to be released into the buffer. We investigated the Hb concentration from one to 48 hours after sampling using three FIT systems.

Method

Hb-positive samples were taken from stools provided for calprotectin analysis.  Five samples were prepared in duplicate using the SENTiFIT pierceTube (Sentinel Diagnostics) and OC-Sensor Autosampling Bottle 3 (Eiken Chemical Co. Ltd.); an additional seven samples were prepared for those two systems and the Extel Hemo-Auto MC Collection Picker (Kyowa Medex Co. Ltd.). Devices were incubated at 19oC and the Hb measured at 1, 2, 3, 24 and 48 hours using the SentiFIT 270, OC-Sensor PLEDIA and HM-JACKarc analysers, respectively. The mean, maximum and minimum percentage differences were calculated.

Results

% Difference in Hb concentration over1-48 hours

OC-Sensor PLEDIA (n=9*)

SentiFIT 270 (n=10*)

HM-JACKarc (n=5*)

Minimum

-22.8

-45.6

11.8

Maximum

27.9

32.9

105.5

Average

9.6

-6.6

58.6

*Some samples excluded as below the analytical range.

Conclusion

Hb concentration over 48 hours showed variation for all systems. The average and minimum percentage differences for the SentiFIT 270 were lower than the PLEDIA, with highest values for HM-JACKarc;  PLEDIA had the lowest maximum percentage difference. The differences may be due to the time taken for the Hb to move from the stick into the buffer and/or differences in sample consistency, bacterial content, age of sample and the detection of different Hb degradation products over time. There was a delay of at least 10 days between when the patient provided stool sample and our FIT analysis. Assessment of a greater number of samples analysed sooner after collection is needed.