Thanks to Peter Howell for suggesting this case.

A 54 year old male, new to the area. On his initial visit to his new Family
Doctor, the Practice Nurse finds glycosuria ++ and a BM-strip blood glucose
of 10.1 mmol/L. An appointment is made by the Family Doctor for him to
attend the laboratory for a glucose tolerance test in three weeks' time.
The following day, the patient 'phones the laboratory to cancel the glucose
tolerance test; and the day after, brings a two-hour GTT blood sample,
taken by the Practice Nurse, to the laboratory. On this sample, the blood
glucose is 2.5 mmol/L

This Case attracted 30 participants and some zoological metaphors.

13 would contact the Practice Nurse;[1.6]
6 would discuss with the Family Doctor.[2.0]

2 participants said 'I smell a rat'
2 participants said 'sounds fishy' (why do fish sound and rats smell?)
1 participant (thank you, James) said 'it has my antennae twitching'.

12 participants queried the validity of the sample (either sample type or
storage conditions);[1.3]
1 would check potassium and phosphate on this sample;[-0.7]
9 queried the nature or the correctness of the GTT [0.8*]
2 queried the validity of the BM stick glucose.[0.5]

4 said 'surprising glucose;[-0.3]
6 queried reactive hypoglycaemia/ dumping syndrome; [0]
2 queried whether the patient was an existing diabetic on oral therapy;[0]
1 queried a drug effect; [-0.3]
1 queried whether the patient had access to insulin; [0.6]
1 queried Munchausen's syndrome; [0.2]
3 queried interference with the sample by the patient; [0.8]
2 asked whether the patient needed life insurance; [-0.3]
1 queried what the patient's job was. [-0.3]
1 said the results were suggestive of DM; [-0.8]
1 thought the patient was likely to have DM. [-0.4]

21 recommended a repeat full GTT under controlled conditions/ done by the
lab; [1.8]
1 recommended a repeat fasting glucose under controlled conditions [1.2]
2 would suggest measuring glycated haemoglobin. [-0.3]

Peter Howell phoned the Family Doctor, who was surprised by the result - he
strongly expected the patient to be a maturity onset diabetic. On the rare
occasions when his Practice carried out their own 'GTT', the patient was
given 360 ml of Lucozade, asked to fast overnight, and come to the Practice
for a blood sample 2 hours after the Lucozade was drunk. This particular
patient was a Heavy Goods Vehicle driver who was waiting to renew his
licence. It was probable that he had cancelled the lab GTT because he
thought that this might show DM, had not drunk the lucozade, and may have
fasted for rather longer than overnight - a later formal GTT confirmed
diabetic status.

Here at the Royal Berkshire Hospital we had a related case a few years ago
- the patient (who presented with abdominal pain) was an airline pilot who
was taking a local remedy (containing 10% lead) to 'cure his diabetes'. I
wonder how common this type of problem is - from a Duty Biochemist
viewpoint, such cases may be very difficult to spot, since all the DB would
usually be faced with is the result from a sample apparently taken two
hours after a glucose load. I suspect in this Case, the patient would have
got away with it had he not cancelled the formal GTT and had not overdone
the fast.

Best wishes
Gordon Challand


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