Cancer Diagnosis Program | Biorepositories and Biospecimen Research Branch

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Evaluation of sample stability for a quantitative faecal immunochemical test and comparison of two sample collection approaches.

Author(s): Mellen S, de Ferrars M, Chapman C, Bevan S, Turvill J, Turnock D

Publication: Ann Clin Biochem, 2018, Vol. 55, Page 657-664

PubMed ID: 29534613 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study compared hemoglobin levels in fecal specimens transferred into specialized collection devices by the patient immediately after collection to levels in specimens transferred after same-day transport at room temperature and short-term refrigerated storage. The effects of storing specimens at room temperature or 4°C for up to one week before transfer on fecal hemoglobin levels was also investigated. Fecal specimens from 137 patients with symptoms suggestive of cancer were collected into standard Sarstedt collection pots and a portion was transferred into Kyowa-Medex collection devices. The main specimen was transported at room temperature (4-9 h) and stored at 4°C for 1-4.5 h before baseline sampling into the collection device. For six patients, specimens were then stored at 4°C or room temperature for 1, 2, 3, and 7 days before transfer to the specialized collection device. Fecal hemoglobin levels were measured on an autoanalyzer in all specimens in a single batch.

   Summary of Findings:

   Large differences in Hb levels were noted between specimens transferred by the patient and those transferred after transport to the laboratory and brief storage with two specimens having much lower levels in the laboratory sampling, two having much higher levels, and two having only small differences in Hb levels. When all 137 specimens were investigated, more specimens had undetectable hemoglobin and fewer 10-400 µg Hb/g or >400 µg Hb/g when sampled after arrival in the laboratory than before transport. Importantly, Hb levels in specimen transferred into the collection device before and after transport were found to not be equivalent using the McNemar test (P<0.05). When simply looking at the 11 of 137 patients with differences in Hb status (positive versus negative) between sampling, 10 were negative  in the laboratory sample and positive in the patient sample but there was no clear effect due to duration of the delay. Further, for the thirteen specimens with quantifiable levels (above the limit of quantification and below the upper limit) in both the sample transferred by the patient and in the sample transferred in the laboratory, Bland-Altman plots showed poor agreement between the two measurements.

   Most specimens had a rapid decline in fecal Hb levels during the first 1-2 days of storage at room temperature or 4°C; however, Hb levels still exceeded ≥10 µg Hb/g feces in five of six specimens stored at room temperature for 2 days or at 4°C for three days, in three of six specimens stored at room temperature for 7 days, and in four of six specimens stored at 4°C for 7 days.

   Biospecimens

   • Bodily Fluid - Feces

   Preservative Types

   • None (Fresh)

   Diagnoses:

   • Diverticulitis
   • Neoplastic - Carcinoma
   • Other diagnoses

   Platform:

   Analyte	Technology Platform
   Protein	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Storage duration	0 days 1 day 2 days 3 days 7 days
   Storage	Specimen transport duration/condition	In collection container In specialized collection device
   Storage	Storage temperature	4°C Room temperature

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