The registered cases are primarily based upon local residents' cases occuring and being diagnosed in the territory, including all types of invasive cancers. Multiple primary sites for the same person are counted separately. Moreover, the cases of carcinoma in-situ of female breast are further collected for monitoring the number of pre-malignant abnormalities.
Quality control measures have been established to monitor the completeness, accuracy and validity of the data. The percentage of morphologically verified cases (MV%), and the percentage of cases identified by death certificate only (DCO%) are two common quality indicators for assessing data completeness. Ideally the MV% and DCO% should be 100% and 0% respectively. In our case, the MV% has reached around 90%, and the DCO% has dropped to less than 0.3% in recent years (For details, please refer to Graphs of Data Quality Indicators). This is already up to the highest standard for developed countries as depicted by the International Agency for Research on Cancer (IARC).
Besides, we apply a series of validation rules on the registered data to ensure accuracy and validity of the data before their release.
When data are collected, specific information identifying the individual patient is needed to check for duplicate registrations. Otherwise, the data would be inaccurate and unsuitable for analysis. The Government's Personal Data (Privacy) Ordinance is designed to protect the privacy of the cancer patient and the use of the related information. It is stated in Principle 3:
Personal data shall not, without the prescribed consent of the data subject, be used for any purpose other than:
(a) the purpose for which the data were to be used at the time of the collection of the data; or
(b) a purpose directly related to the purpose referred to in paragraph (a).
In the meantime there is an exemption clause for 'Statistics and Research' under Section 8.62:
Personal data are exempt from the provisions of data protection principle 3 where:
(a) the data are to be used for preparing statistics or carrying out research;
(b) the data are not to be used for any other purpose; and
(c) the resulting statistics or results of the research are not made available in a form which identifies the data subjects or any of them.
All our staffs understand and are bound by the Privacy Ordinance before beginning work with the Registry. All data are surrounded with appropriate security and no un-authorized person is allowed to access the computer system. Only aggregate rates and numbers are reported.
For more information, please visit the Office of the Privacy Commissioner for Personal Data, Hong Kong homepage at www.pcpd.org.hk.