Detection bias:structural analysis of different study designs / 上海预防医学

Detection bias is an information bias.It was first proposed by Horwitz from the study investigating the association of the administration of estrogen after menopause with the occurrence of endometrial cancer, which still prevails in most epidemiological studies.We use the Directed Acyclic Graph to analyze the effect of a given exposure on a specific outcome with the association estimates between the measured exposure and outcome.Detection bias occurs when there is additional open paths irrelevant to the target path of interest which is originated from measured exposure to measured outcome.We further analyzed how the detection bias was formed under different study designs, including cohort study, randomized clinical trial and case-control study in order to further investigate its potential influence on the effect/association estimation.

Detection bias:structural analysis of different study designs / 上海预防医学

Detection bias is an information bias.It was first proposed by Horwitz from the study investigating the association of the administration of estrogen after menopause with the occurrence of endometrial cancer, which still prevails in most epidemiological studies.We use the Directed Acyclic Graph to analyze the effect of a given exposure on a specific outcome with the association estimates between the measured exposure and outcome.Detection bias occurs when there is additional open paths irrelevant to the target path of interest which is originated from measured exposure to measured outcome.We further analyzed how the detection bias was formed under different study designs, including cohort study, randomized clinical trial and case-control study in order to further investigate its potential influence on the effect/association estimation.

Increased risk of thyroid cancer in female residents nearby nuclear power plants in Korea: was it due to detection bias?

BACKGROUND: The Korea Radiation Effect & Epidemiology Cohort METHODS: Using the KREEC-R raw data, we calculated age standardized rates (ASRs) of female thyroid cancer and re-analyzed the results of survey on the use of medical services. We also marked the administrative districts of residents who received the Radiation Health Research Institute (RHRI) health examinations and those in which thyroid cancer case occurred as per the Chonnam National University Research Institute of Medical Sciences (RIMS) final report on maps where the locations of NPPs and 5 km-radii around them were also indicated. And we compared the incidence rates of Radiation-induced cancer measured between the first period when RHRI health examinations were not yet implemented, and the second period when the RHRI health examinations were implemented. RESULTS: The ASR for the far-distance group, which comprised residents living in areas outside the 30 km radius of the NPPs, increased rapidly after 2000; however, that of the exposed group, which comprised residents living within a 5 km radius of the NPPs, started to increase rapidly even before 1995. The frequencies of the use of medical services were significantly higher in the intermediate proximate group, which comprised residents living within a 5–30 km radius of the NPPs, than in the exposed group in women. In case of female thyroid cancer, the second period ASR was higher than the first period ASR, but in case of female liver cancer and female stomach cancer no significant difference were observed between the periods. On map, many administrative districts of residents who received RHRI health examinations and most administrative districts in which thyroid cancer case occurred on RIMS final report were outside 5 km-radii around NPPs. CONCLUSIONS: We could not find any evidence supporting the assertion that detection bias influenced the increased risks of female thyroid cancer observed in the exposed group of the KREEC-R study, as opposed to the control group.

Influence of camera-trap sampling design on mammal species capture rates and community structures in southeastern Brazil

The distribution of species and population attributes are critical data for biodiversity conservation. As a tool for obtaining such data, camera traps have become increasingly common throughout the world. However, there are disagreements on how camera-trap records should be used due to imperfect species detectability and limitations regarding the use of capture rates as surrogates for abundance. We evaluated variations in the capture rates and community structures of mammals in camera-trap surveys using four different sampling designs. The camera traps were installed on internal roads (in the first and fourth years of the study), at 100-200 m from roads (internal edges; second year) and at 500 m from the nearest internal road (forest interior; third year). The mammal communities sampled in the internal edges and forest interior were similar to each other but differed significantly from those sampled on the roads. Furthermore, for most species, the number of records and the capture success varied widely among the four sampling designs. A further experiment showed that camera traps placed on the same tree trunk but facing in opposing directions also recorded few species in common. Our results demonstrated that presence or non-detection and capture rates vary among the different sampling designs. These differences resulted mostly from the habitat use and behavioral attributes of species in association with differences in sampling surveys, which resulted in differential detectability. We also recorded variations in the distribution of records per sampling point and at the same spot, evidencing the stochasticity associated with the camera-trap location and orientation. These findings reinforce that for species whose specimens cannot be individually identified, the capture rates should be best used as inputs for presence and detection analyses and for behavior inferences (regarding the preferential use of habitats and activity patterns, for example). Comparisons between capture rates or among relative abundance indices, even for the same species, should be made cautiously.

A distribuição das espécies e os atributos das populações são dados críticos para a conservação da biodiversidade. Enquanto ferramenta para obtenção de tais dados, as armadilhas fotográficas tem se tornado cada vez mais comuns em estudos em todo o mundo. No entanto, há divergências sobre como os registros fotográficos devem ser utilizados devido a problemas de detectabilidade e limitações relacionadas ao uso das taxas de captura como substitutos de abundância. No presente estudo foram avaliadas variações na taxa de captura e na estrutura da comunidade de mamíferos registrada por meio de armadilhas fotográficas utilizando-se quatro diferentes desenhos amostrais. As armadilhas foram instaladas em estradas internas (primeiro e quarto anos), a 100-200 m de distância das estradas (bordas internas; segundo ano) e a 500 m da estrada mais próxima (interior da mata; terceiro ano). As comunidades de mamíferos amostradas em bordas internas e interior da floresta foram semelhantes entre si, mas diferiram significativamente daquelas amostradas em estradas. Além disso, para a maioria das espécies, o número de registros e o sucesso de captura variaram muito entre os quatro desenhos amostrais. A partir de um experimento desenvolvido paralelamente às amostragens, foi observado ainda que armadilhas fotográficas colocadas em um mesmo tronco de árvore, mas voltadas para direções opostas, registraram poucas espécies em comum. Nossos resultados demonstram que presença ou não detecção e taxas de captura variam entre diferentes desenhos de amostragem. Essas diferenças são atribuídas principalmente ao uso do habitat e atributos comportamentais das espécies, em associação com diferenças no desenho amostral, resultando em diferenças na detectabilidade. Foram também registradas variações na distribuição de registros entre pontos de amostragem e para o mesmo local, evidenciando a estocasticidade associada à localização e orientação das armadilhas. Esses dados reforçam que, para espécies cujos espécimes não podem ser individualmente identificados, os registros fotográficos são mais bem utilizados como insumo para análises de presença e detecção, assim como para obtenção de informações relacionadas a comportamento (uso preferencial de habitats e padrão de atividade, por exemplo). Comparações entre taxas de captura ou índices de abundância relativa, mesmo para a mesma espécie, devem ser realizadas com cautela.