Essentially health screening is looking for a particular condition before you have any symptoms.  A small sample of your blood, cells or breast tissue (via X-ray) are checked for the likelihood of developing these symptoms.Screening is conducted in the best interest of protecting your health.  Most people take part in screening in order gain reassurance they are healthy, rather than with the expectation they are not.

Screening increases your chances that a condition:

• will be avoided
• detected early
• or be curable

Screening sorts people into two groups: people who have an increased chance of having a particular condition (positive screening result) and people who do not have an increased chance of having the condition (negative screening result).  

Whilst screening reduces your risk of developing or dying from a disease, it is important to remember that it is not a guarantee of prevention, or of diagnosis and cure.

What are the benefits of screening?
Screening programmes detect some conditions, reduce your chance of developing or dying from some conditions and can improve your quality of life. In some cases (for example, breast screening), screening may detect cancer at an early stage. In others (such as newborn metabolic screening) screening may find conditions, which can be treated before the baby develops a preventable illness or disability.

What results should I expect from my screen?
Screening does not give you a diagnosis and it doesn't tell you whether you do have the condition.  If you have a positive screening result, you will be offered a diagnostic test, which will determine whether you do have the condition. 

If you have a negative screening result, you will not be offered this test.  Depending on the type of screening, you may be invited to come back for screening at a later date e.g. for a repeat cervical smear test.

I have heard that there are risks associated with screening.  What are they?
All screening has benefits, costs, and harms.  There is an ethical obligation to minimise harm and the overall benefits should outweigh any harm that results from screening.

However accurate a screening test may be, there will always be someone who has the disease but does not get picked up by the test. These so-called false negatives can lead you to believe that you are healthy, when you are not.

A false positive is when a person who does not have the condition is put into the group of people who have an increased chance of having the condition. False positives can result in increased anxiety and referral to diagnostic tests.

Who manages the screening process in New Zealand?
The National Screening Unit (NSU) is a division of the Ministry of Health, which is currently responsible for four screening programmes:

• BreastScreen Aotearoa - screens women for breast cancer
  
• National Cervical Screening Programme - screens women for abnormal changes to cells on the cervix
  
• Newborn Metabolic Screening Programme - screens newborn babies for certain metabolic disorders
  
• Antenatal HIV Screening Programme - screens pregnant women for HIV to reduce the chances of HIV being passed to the baby
  
• Universal Newborn Hearing Screening Programme - screens newborn babies for hearing loss.  This programme will be offered in some regions from July 2007 with nationwide implementation by 2009.

Are there any other diseases that could soon be screened in New Zealand?
The National Screening Unit (NSU) is also responsible for providing policy advice to Government regarding future screening programmes.

In 2007, policy work is being carried out on antenatal screening for down syndrome and colorectal cancer screening.  In December 2006, the report Chlamydia Screening in New Zealand: Report for the National Screening Unit was published by the NSU.  Currently, the NSU does not run a screening programme for Chlamydia.  

he NSU is not currently undertaking any work on prostate cancer screening.