Our team of experts answer your queries on biochemistry, diving and IVD.
What is the best way to investigate a persistent slightly raised alkaline phosphatase level in a woman over 60?
Alkaline phosphatase is present in high concentrations in the liver, bone (osteoblasts), placenta and intestinal epithelium. These tissues each contain their own isoenzymes of the enzyme.
Pathological increases in alkaline phosphatase activity are most often seen in cholestatic liver disease and in bone diseases in which there is an increase in osteoblastic activity, such as Paget's disease and osteomalacia.
Alkaline phosphatase activity can be slightly higher than normal in apparently healthy people as they get older.
This may reflect the high incidence of mild, sub-clinical Paget's disease in elderly patients. The increase becomes noticeable in women during the menopause.
Some 95 per cent of women aged under 45 have an alkaline phosphatase level below 88. Levels then gradually rise and in those over 71 years of age, 95 per cent have a level below 135.
Alkaline phosphatase is often measured as part of a biochemical profile, and a raised level is commonly found in the absence of clinical evidence of bone or liver disease, or other biochemical abnormalities. If the clinical situation requires further investigation, a simple test is to measure gamma-glutamyl transferase.
This enzyme is found in the liver, but not in bone, and its serum activity is often, but not always, increased when there is an excess of hepatic alkaline phosphatase in the sample.
To establish the exact origin of the alkaline phosphatase, the laboratory may measure the tissue-specific isoenzymes, by techniques such as electrophoresis and differential heat inactivation.
Dr Garry John, consultant clinical biochemist at Norfolk and Norwich University Hospital
A patient has asked for a medical to go diving. Three years ago, he had a ligation of his external carotid artery as an emergency after suffering severe left-sided epistaxis. Is this a relative or absolute contraindication to diving?
Ligation of the external carotid is performed only where all else has failed to stem the bleed from epistaxis. It is a permanent procedure that stops the blood flow directly to Little's area on the nasal septum.
This should not cause any problems when scuba diving. There is still adequate blood flow to the head and brain through the internal carotid artery, so there should be no risk of fainting or light-headedness under water.
In fact, the reduced blood supply to the nasal mucosa may actually prevent a common diving problem: nosebleeds after forced equalisation.
The diving regulations always say never to dive with a cold, but try telling that to a diver in denial on the last day of his holiday. He will dive anyway, and the pressure needed to blow air past a blocked Eustachian tube can pop a vessel in the nose.
The resulting blood in the mask and surrounding water may not interest the sharks, but it does attract smaller fish.
Dr Jules Eden, medical examiner of divers, south London
If screening swabs show asymptomatic bacterial vaginosis, is insertion of an IUD contraindicated?
How common is bacterial vaginosis as a cause of pelvic inflammatory disease (PID)?
In the UK, about half of cases of acute PID are due to Chlamydia trachomatis.
The other main cause of PID is Neisseria gonorrhoeae.
However, anaerobes such as those causing bacterial vaginosis have also been implicated in PID.
Bacterial vaginosis is caused by a change in the normal vaginal flora, rather than a specific bacterial infection.
It is present in up to 20 per cent of women and causes a fish- or onion-smelling discharge, which may appear or be worse after sex or menstruation.
It is associated with the use of douching and bath additives.
Bacterial vaginosis is associated with an increased risk of mid-trimester miscarriage and premature labour, and so it is usually treated if it is found in pregnancy.
I am not aware of any direct evidence about bacterial vaginosis on its own in relation to IUD insertion. However, it would seem sensible to treat it before putting instruments through the cervix, so I would be inclined to give a course of metronidazole 400mg twice daily for five days.
An alternative, which might be more practical if the IUD needs to be fitted as soon as possible, is to give a single dose of 2g of metronidazole.
Since bacterial vaginosis does not seem to be sexually transmitted, there is no need to treat the partner.
Dr Anne Szarewski, clinical consultant at the Wolfson Institute of Preventive Medicine.