Background: The Japan Nurses' Health Study (JNHS) is a large-scale, nationwide prospective cohort study of female nurses. This study aimed to examine the validity of self-reported diagnosis of cancer among the JNHS cohort members (N=15,019).
Methods: For women who reported any diagnosis of five cancers (stomach, colorectal, liver, lung and thyroid) in the biennial follow-up surveys, an additional outcome survey, medical facility survey, and confirmation of death certificate (DC) were conducted. The JNHS Validation Study Committee (referred to as "the committee") made a final decision on the reported outcomes. To examine the validity of self-reported diagnosis of cancer, the positive predictive value (PPV) was calculated using the committee's decision as the gold standard. To examine the validity of the committee's decision based on self-reports and DCs, PPV was calculated using physician-reported information as the gold standard.
Results: The PPV of self-reported diagnosis in the biennial follow-up surveys was 77.8% for stomach, 66.2% for colorectal, 41.7% for liver, 60.2% for lung, and 64.6% for thyroid cancer. The corresponding PPVs in the additional outcome survey were 96.2%, 80.7%, 62.5%, 82.5%, and 96.9%, respectively. The PPV of the committee's decision was 100% for stomach, 87.5% for colorectal, 94.7% for lung, and 100% for thyroid cancer (data not available for liver cancer). The proportion of DC-only cases among committee-defined cases was below 10% for all cancers except liver cancer (28.6%).
Conclusions: The validity of identifying cancer diagnosis based on self-reported information in the JNHS was favorable for stomach, colorectal, lung and thyroid cancer.
Keywords: Cohort studies; Neoplasms; Validity; women’ s health.