Dr John P Wright
Updated: 22 May 2007
The purpose of investigations is firstly to confirm a hypothesis and thereby make a diagnosis. If an investigation is done without a hypothesis it becomes at best a poorly conceived screening test which may occasionally hit the jackpot similar to the now defunct Lotto.
Secondly it is to sanction a therapeutic option. If patient management will not change after the test result is to hand the test is at best a confirmation of the original diagnosis. This is called over servicing.
In some instances we over service because we are over serviced. We want to know the haemoglobin and we get the full morphology, white cell count and even platelets. We want to know if the patient has acute hepatitis and we get the LDH and globulin. Clearly we should ask for what we want but we are seduced by the ease of a tick and the respect shown by the technician phoning us to report an increased “red cell distribution width”.
More pertinent is our requesting of inappropriate investigations. The three main offenders appear to be abdominal ultrasound, Helicobacter pylori serology and CEA.
There is no doubt that abdominal ultrasound is an excellent method of examining the abdomen to confirm the clinical impression of gallbladder pathology, aortic aneurysm, renal and ovarian cysts and the occasional unsuspected pregnancy. From these virtues it is clear that the benefit of abdominal ultrasound in the presence of gastrointestinal symptoms is extremely limited. The R440.00 could be better spent on taking a fuller history or even a “therapeutic trial of medication” for the hypothesis/diagnosis. The pious hope that we may find a pancreatic or colon cancer is almost farcical. If these diagnoses are seriously considered a CAT scan or colonoscopy needs to be performed. Even more bizarre is the performing of an abdominal ultrasound as the primary investigation for iron deficiency anaemia. We could all add our personal favourite to this list of our colleague’s foibles.
The second most inappropriate investigation is Helicobacter pylori serology to elucidate the cause of abdominal symptoms. The popularity of this test probably relates to it being available and inoffensive unlike other serology which is underutilized. The second promoter of HP serology is “Dyspepsia Protocols” particularly from Europe where the incidence of positive tests in the general population is less than our 60%. Furthermore if the patient has dyspepsia (i.e. epigastric pain or discomfort aggravated or relieved by food) and not heartburn or cramping pain, a positive HP serology simply increases the chances that a duodenal ulcer might be present. Helicobacter pylori infection is in itself an unusual cause of dyspepsia. The commonest cause of dyspepsia is non-ulcer dyspepsia which will respond quite dramatically to a week or two of acid inhibition with H2 antagonists or a PPI. Both these options cost less than the Helicobacter pylori serology (R99.90) and relieve the symptoms!
The third offender is the CEA. This is a useful test for the monitoring of cancer of the colon but as a diagnostic test it appears inappropriate. At a cost of R154.20 one has to decide what to do if the test is negative. A positive test simply means a colonoscopy is indicated as the false positives would have been considered before ordering the investigation. If a patient has colonic symptoms sufficient to include a colonic cancer in the differential then a colonoscopy is probably already indicated and needs to be performed.
When all three of the ugly sisters have been done at R694.10 and no diagnosis is made the patient is often reassured and given a symptomatic generic and probiotic which takes the total bill up to R1000.00.
The well used phrase “evidence based medicine” may well be viewed as a step to far…