Primary Health Care - JOHN J. HADDAD, Ph.D.

The ‘ologies’ (underpinning academic disciplines) of primary health care 27
Box 2.1 Examples of how epidemiology can help in the clinical
encounter.
A 24-year-old woman with a history of epilepsy is surprised to be expecting
her first child, and asks her GP whether she should stop her tablets (or change
to a different medication) to reduce the risk of drug-related damage to her
unborn baby. The GP contacts the pharmaceutical company’s medical adviser,
who consults their international database of post-marketing surveillance data
on the safety of the drug in pregnancy.
A 39-year-old woman seeking family planning advice asks the nurse ‘is the
oral contraceptive pill safe for me?’. The nurse consults a set of risk tables based
on large population cohorts which take account of age, smoking status, blood
pressure and other risk factors, before advising the patient on her chance of
developing side effects.
A 76-year-old man who lives an active and independent life has a mild stroke
and is found to have an irregular heartbeat (atrial fibrillation). His physician
recommends that he take warfarin to ‘thin the blood’, thereby preventing further
strokes. But the man is reluctant to have the weekly blood tests required
for warfarin therapy and asks just how much his risk of stroke is going to
change if he takes the drug. His GP consults the Cochrane database for evidence
from randomised controlled trials and is able to provide the necessary
information for the man to make an informed choice about whether the blood
tests are worth the inconvenience.
I do not plan in this book to give a comprehensive overview of either general
epidemiology or clinical epidemiology (EBM). Rather, this section will highlight
the key theoretical concepts that underpin these disciplines. For general
epidemiology, Geoffrey Rose’s Epidemiology for the Uninitiated (now revised by
Coggon) 8 offers an accessible introduction to the basics; and Barbara Starfield’s
Primary Health Care provides a weighty application of these principles to the
specific disease patterns relevant to the primary care clinician. 9 For a basic introduction
to clinical epidemiology, you might try my own book How to Read
a Paper – the Basics of Evidence Based Medicine 10 ; for a more detailed introduction
I recommend Fletcher et al.’s Clinical Epidemiology – the Essentials; and for
those after a ‘black belt’ in EBM, Sackett and colleagues’ big red book Clinical
Epidemiology 11 is still unparalleled. Mark Gabbay’s Evidence Based Primary Care
Handbook repackages the concepts of EBM focusing specifically on primary
care examples. 12
Let us briefly consider the key concepts and theoretical framework within
which epidemiology (and therefore evidence-based medicine) makes sense.
The first thing to say is that EBM is predicated very strongly on the biomedical
model described in the previous section. The second concept to highlight is
the role of mathematics (especially probability theory) in informing decision
making. Dave Sackett, who I believe deserves more credit than anyone else
for popularising EBM, produced what is probably the most widely quoted