Identification of high‑risk and low‑risk clusters and estimation of the relative risk of acute lymphoblastic leukemia in provinces of Iran during 2006–2014 period: A geo‑epidemiological study

Background: The present study was conducted to determine the epidemiological status, identify high‑risk and low‑risk clusters, and estimate the relative risk (RR) of acute lymphoblastic leukemia (ALL) in provinces of Iran. Materials and Methods: This is an ecological study carried out using an Exploratory Multiple‑Group design on 3769 children under 15 years of age with ALL from 2006 to 2014. Data analysis was performed using Mann–Whitney U, Global Moran’s I and Kuldorff’s purely spatial scan statistic tests at a significance level of 0.05. Results: The average annual incidence rate of ALL during 2006–2014 period was 2.25/100,000 children under 15 years of age. The most likely high‑risk cluster with log‑likelihood ratio (LLR) =327.47 is located in the southwestern part of Iran with a radius of 294.93 km and a centrality of 30.77 N and 50.83 E, which contained 1276 patients with a RR of 2.56. It includes Fars, Bushehr, Kohgiluyeh and Boyer‑Ahmad, Khuzestan and Chahar Mahall and Bakhtiari provinces. On the other hand, the most likely low‑risk cluster with 517 patients, and a RR 0.49 and LLR = 227.03 was identified in the northwestern part of Iran with a radius of 270.38 km and a centrality of 37.25 N and 49.49 E. It includes Zanjan, Qazvin, Gilan and East Azerbaijan, Ardabil, Alborz and Tehran provinces. Conclusion: High‑risk clusters were observed in Southwestern, central, and eastern Iran, while low‑risk clusters were identified in Northern and Western Iran.