A 30-year epidemiologic survey (1974-2003) of haematological malignancies on the island of Sardinia: temporal changes in incidence and a geographic comparison of incidence rates.

In a previous survey of newly diagnosed haematological malignancies (HMs) in Sardinia from 1974 to 1993, we observed a marked increase in the incidence of many HMs that we chiefly attributed to improvements in case ascertainment. To better define the nature of this increase, we extended the survey by an additional decade (1994-2003), applying the same previously used methods. The incidence of HMs further increased from 1994 to 2003. The incidence rate of total HMs (THMs), standardised to the world population, was 30.15 × 10(5) person-years vs. 21.58 from 1984 to 1993 and 15.26 from 1974 to 1983. The temporal variations in the incidence differed in different HMs and were correlated with the diseases clinical characteristics and the increased availability of diagnostic tools and skills in Sardinia. These observations support the hypothesis that the temporal differences in the incidence rates observed for many HMs in Sardinia over the 30-year survey period were caused by temporal differences in diagnostic efficiency rather than by disease occurrence. An important exception was the increase in non-Hodgkin's lymphoma, which represents a true increase in occurrence, similarly to most Western countries. The incidence rates of HMs already having or reaching stable values in the decade 1994-2003 were similar to those of most Western countries. No significant evidence emerged to suggest that Sardinian particularities influenced the occurrence of HMs. This study demonstrates the extent to which diagnostic efficiency can influence incidence evaluations and emphasises the importance of prolonged observation to determine the validity of incidence rates for both temporal and geographic comparisons.