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The evidence basis needed for developing screening policies

Diagnosis and Screening: The evidence basis needed for developing screening policies and implementing screening programmes, including established programmes such as breast and cervix and those currently in development, being piloted or subject to major research activity, current examples (amongst others) being colon cancer, chlamydia screening and certain antenatal/ neonatal screening tests

Health Technology Assessment

Health technology assessment (HTA) uses evidence to promote health and prevent and treat disease.  HTA includes the implication of heath technology to improve health outcomes.  It asks whether technology provides benefits for the population and if it presents value for money.

The evidence basis for screening is whether early detection is beneficial, and if persons identified with early-state disease detected through screening have better health outcomes than those who come to clinical attention without screening. It is not enough to know that a screening test actually identifies early diseases or conditions at a specific point of disease development. There must also be an effective intervention, which itself must be scientifically assessed.

The evidence to support or refute particular screening programmes is often limited.  This may be because of the complexity of the screening issue, or the rarity of the conditions being screened for.  The best evidence for screening comes from randomised controlled trials (or meta-analysis of RCTs).

Table 3.8.1 SCREENING TESTS THAT CAN BE HARMFUL

Screening test

Proposed benefits

Potential harms

Whole-body computerised tomography (CT)

To rule-out undiagnosed diseases

High radiation dose

Unlikely to prevent disease

Whole-body magnetic resonance imaging (MRI)

To rule-out undiagnosed diseases

No radiation dose, but raised chance of false alarms of nodules in lung, cysts in liver, etc.

Exercise electrocardiogram (ECG)

Screening for heart problems

Benefit is limited to only some people with heart disease, but not for healthy people

Prostate Specific Antigen (PSA)

Early detection of prostate cancer

Many false alarms due to benign tumours, leading to unnecessary and potentially harmful medical procedures. No evidence that mortality is reduced.

Mammography under 50 years old

Early detection of breast cancer

False alarms in low prevalence population

Source: Adapted from Types of Screening that can do more harm than good, Angel Raffle (2006)

Table 3.8.2 Screening programmes under development in the UK (as of June 2008)


Condition

Description of programme

Status

Antenatal

 

 

Familial Dysautonomia*

Not currently offered

Ongoing review by NSC

Predictors of preterm labour

Not currently offered

HTA review ongoing

Streptococcus B

Not currently offered

Being considered by NSC

Thrombophilia**

Not currently offered

Being considered by NSC

Newborn Babies

 

 

Amino acid metabolism disorder screening

Not currently offered

Being considered by NSC

Medium chain acyl CoA dehygrogenase deficiency (MCADD)

Should be offered to all babies

Offered to all babies in England by March 2009 (not Scotland, Wales, NI)

Cannavan's disease †

Not currently offered

Being considered by NSC

Congenital heart disease

Not currently offered

HTA review ongoing

Cystic fibrosis

Should be offered to all babies

Phased implementation across the UK by 2008

Adults

 

 

Abdominal aortic aneurysm

Should be offered to all men aged 65+, but with clear information of risk of elective surgery, and need to develop vascular surgical services

Implementation of a screening programme is being planned for roll-out over the next 5 years

Anal cancer

Not currently offered

HTA review ongoing

Bowel cancer

Currently offered to men and women aged 50+

Began in Jul. 2006 and phased in by Dec. 2009

Deafness

Not currently offered

Being considered by NSC

Domestic violence

Not currently offered

Ongoing review by NSC and Home Office

Prostate cancer

Can be offered if the man fully understands the lack of good quality evidence about the benefits and risk of testing

HTA is conducting a trial of prostate cancers detected at an early stage

Vascular risk

Should be offered to whole population

A Vascular Risk Management Programme is being introduced

HTA: Health Technology Assessment

* Disease or malfunction of the autonomic nervous system
** Propensity to develop thrombosis
† Progressive degenerative disease of nerve cells in the brain

Reference Materials

  1. Oortwijn W, David Banta H and Cranovsky R. Introduction: mass screening, health technology assessment, and health policy in some European countries

  2. International Journal of Technology Assessment in Health Care. 2001:17;269-274

  3. UK National Screening Committee's Policy Positions, June 2008 http://www.nsc.nhs.uk/pdfs/

© Dr Murad Ruf and Dr Oliver Morgan 2008