Data on five allergic conditions were abstracted from the medical records of 180 cases of childhood acute lymphoblastic leukaemia (ALL) and 718 matched controls. Odds Ratios (OR) and 95% Confidence Intervals (CI) were estimated for composite variables and for individual allergies using conditional logistic regression modelling. Allergies were divided into late and early diagnoses (those made within the year before the matched case's ALL diagnosis and those made earlier, respectively). Among the early diagnoses, atopy or hives was significantly associated with ALL (OR=2.20; 95% CI: 1.16-4.16). Significant associations were found for late diagnoses of atopy or hives (OR=3.78; 95% CI: 1.00-14.29) and of asthma (OR=3.10; 95% CI: 1.39-6.95). None of the other allergic conditions were associated with ALL. These results are contrary to those of prior studies of childhood ALL and allergy.
Bibliographical noteFunding Information:
We identified cases and controls through the databases of four health maintenance organisations (HMOs) in the Western United States: Kaiser-Permanente Health Systems in Southern and Northern California and Oregon (SCK, NCK, and NWK, respectively), and the Group Health Cooperative (GHC) of Puget Sound. These four HMOs contribute data to the Vaccine Safety Datalink Project, which is sponsored by the National Immunization Program of the Centers for Disease Control and Prevention  . Cases were children aged 6 years or younger who were diagnosed with ALL (International Classification of Diseases (ICD)-9 code 204.0) between 1985 and 1999, and born in 1983 or later. A pathologist, blinded to the exposure status, reviewed case laboratory reports to confirm a diagnosis of ALL and, when possible, to classify the subtype of ALL into B- or T-cell lineages. Controls were individually matched to cases on HMO, gender and date of birth (within 2 weeks) and, in addition to meeting the eligibility criteria, must have been enrolled at the time of the matched case's diagnosis. To be eligible, subjects must have enrolled in their HMO within 90 days of birth (extended to 180 days at the Southern California Kaiser) and must have been continuously enrolled up until the earlier of either the matched case's date of diagnosis or 2 years of age. Professional abstractors employed by the HMOs collected information regarding demographics (race, ethnicity, sibship and gender), birth variables (birth weight, gestational age and maternal age at birth of subject), and vaccination history from the subject's medical charts. Five categories of allergies—asthma, atopy or hives, eczema, food-drug-bee allergy (FDBA), and pollen-dust-dander allergy (PDDA)—and the dates of their first diagnosis were also recorded. Allergies were recorded if they were diagnosed by a physician, either within the HMO or without, and had a month and year of diagnosis. Day was assigned a value of 15 if missing. Subjects were presumed not to have an allergic condition if no mention of diagnosis was made in the medical chart.
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- Case-control study
- Childhood leukaemia