Does the environmental temperature influence all screening programs for colorectal cancer?

Background-aim: In previous studies it has been described that the increase in environmental temperature decreases the values of hemoglobin in faeces (f-Hb)increasing the rate of false negatives. Each colorectal cancer (CRC)screening program uses a different model, so it is important to know how temperature can affect different models. The objective of this study is to see if the environmental temperature affects the result of f-Hb in our working model. Methods: A retrospective study of all f-Hb results from the CRC screening program obtained in two different areas of our population during the years 2016 and 2017 was made: group 1 mean temperature 14.2 °C (−6.5 to 39 °C), group 2 mean temperature 12.8 °C (−2.9 to 37 °C). The average daily temperatures recorded on the day of the analysis of the samples in the Laboratory and the average temperature during the summer and winter months were correlated with the results of f-Hb and the percentage of positivity of the fecal occult blood test (SOH)(cut-off point 100 μg Hb/L). The analyzer used was OC-Sensor DIANA - Palex Medical. Results: A total of 19,315 results were collected (group 1: 8423, group 2: 10892). When correlating the months of highest average temperature (June–July, group 1: 22 °C, group 2: 19.8 °C)with the months of lowest temperature (November–December, group 1: 5.4 °C, group 2: 8.4 °C)it was observed that the values of f-Hb were higher in the months of higher temperature (group 1: 31 vs 22 μg Hb/L, group 2: 25.2 vs 18.1 μg Hb/L). In addition, when analyzing the results of f-Hb in different cut-off points of medium temperature, it can be seen in group 1 that to higher temperature the f-Hb value increases (> 15 vs <15 °C: 26.2 and 25.3 μg Hb/L; > 20 vs <10 °C: 29.4 and 22.1 μg Hb/L; > 25 vs <5 °C: 25.9 and 11.6 μg Hb/L); although in group 2 this pattern was not observed. The positive (SOH)test percentages in the different comparison groups did not show important differences. Conclusions: The results obtained in our study show that in CRC screening models like ours, where the SOH kits are delivered by the participants in their primary care center and from there they are sent to the Laboratory and analyzed on the day of their arrival, increases in ambient temperature do not seem to increase the false negative rate. This study presents several biases such as not recording the temperatures prior to the analysis of the kit in the Laboratory, nor the patient's round number; but it serves as a first step of recruitment for a prospective study.