Delayed sample arrival at the laboratory does not lead to more false negatives in the Danish population screening for colorectal cancer.
Author(s): Hansen AT, Hoffmann-Lücke E, Nielsen BK, Reinholdt B, Hindersson P, Heidemann K, Hornung N
Publication: Scand J Clin Lab Invest, 2017, Vol. , Page 1-4
PubMed ID: 28933963 PubMed Review Paper? No
Purpose of Paper
This paper investigated the effects of storage and patient age and gender on immunochemical fecal occult blood test (iFOBT) results.
Conclusion of Paper
Mean iFOBT levels increased by 23% after storage at 30˚C for 14 days and smaller changes were noted after storage at room temperature for up to 13 days. The rate of false positives increased 27% after storage at 30˚C and 10% after storage at room temperature, but there was no effect on the false negative rate. The percentage of positive and negative results was unaffected by an increase in the acceptable shipping time to 5 days. The percentage of positive results was higher in males than females and also increased with patient age.
Studies
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Study Purpose
This study investigated the effects of storing feces at 30˚C or room temperature on the percentage of false negative and false positive iFOBT results. Stool specimens from 60 patients were analyzed on day 0 and again after 14 days at 30˚C. The amount of hemoglobin in feces was determined by the immunochemical iFOBT testing. Specimens were selected such that a range of values was present in specimens tested on day 0. Stool specimens from 10 patients with initial iFOBT values close to the cut-off for positivity were analyzed on day 0 then every other day during 13 days of storage at room temperature.
Summary of Findings:
The mean concentration of iFOBT increased during 14 days of storage at 30˚C by 23% (31 µg/L, range -135 µg/L to 170µg/L), but for individual specimensthe maximal decreases (-72 µg/L) and increases (89 µg/L) were smaller when stored at room temperature for 13 days. Sixteen (27%) of the negative specimens were positive after storage at 30˚C and one (10%) of the negative specimens was positive after storage at room temperature for 13 days, but none of three positive specimens turned negative.
Biospecimens
Preservative Types
- None (Fresh)
Diagnoses:
- Not specified
Platform:
Analyte Technology Platform Protein Immunoassay Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Storage Storage duration 0 days
14 days
Storage Storage temperature Room temperature
30˚C
Storage Time at room temperature 0 days
1 days
3 days
5 days
7 days
9 days
11 days
13 days
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Study Purpose
This study investigated the effects of allowing a longer lag time between collection and laboratory arrival on the false positive rate of iFOBT in Danish patients. The effects of patient age and gender were also examined. The false positive rates were compared for 104,328 patients before (69,633 patients) and after (34,695 patients) the acceptable transport time was increased from a time point not specified by the authors to 5 days. The presence of hemoglobin was determined using the iFOBT assay.
Summary of Findings:
iFOBT was more likely to be positive in males than females and the percentage of positives increased with increasing patient age. Importantly, the percentage of positive and negative results was comparable before and after the acceptable lag time was changed, regardless of patient age or gender.
Biospecimens
Preservative Types
- None (Fresh)
Diagnoses:
- Not specified
Platform:
Analyte Technology Platform Protein Immunoassay Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Storage Specimen transport duration/condition Unspecified shorter duration
< 5 days
Preaquisition Patient gender Female
Male
Preaquisition Patient age 60-69 years
>70 years
50-59 years