TB or not TB?

There has been a brief window in the UK during which we may have allowed ourselves to forget about tuberculosis. Now that prevalence is rising, especially in inner cities, it is time to rethink. This month, Milburn et al (page 386) report an outbreak of infections, including active disease, in a private London nursery school serving 38, 2–4 year olds. An employee, newly arrived from an endemic area, infected 11 of the children and eight needed antituberculosis chemotherapy.

The authors recommend screening for TB those who come from areas of high prevalence and are in close contact with vulnerable populations such as young children. Unvaccinated tuberculin negative contacts must be retested and the importance of neonatal BCG vaccinations is emphasised. The authors do not deal with the current problems with vaccine supply in the UK. This should be of great concern to us all.

OTC not OTT

Bird droppings are white and damage the paintwork on your car because of their high uric acid content. This is because birds are unable to excrete ammonia as urea because it would be impossible to fly with a full bladder. Fish, on the other hand, don't need to metabolise ammonia at all as their gills function as a dialyser, which is why fish smell of ammonia after death (Bell R, personal communication), Finns (and the rest of us) need ornithine transcarbamylase to do the job. This month, Schultz and Salo (page 390) remind us that OTC deficiency can first present beyond infancy and delayed diagnosis can be fatal. They describe three such children, two of whom are boys, initially thought to have suffered encephalitis, sibling rivalry and defiant behaviour, respectively.

The message is to measure plasma ammonia, amino acids and transaminases in children with symptoms such as rage, fury, confusion or odd behaviour, especially after infection, injury or a high protein meal. It's lucky this paper wasn't published when my children were in their teens or they might have found themselves undergoing venepuncture.

Sweat, toil, and a few tears

Dr Jean Kirk, from Edinburgh, has audited 30 laboratories carrying out sweat testing for cystic fibrosis (CF) (page 425). This apparently simplest of investigations proves to have hidden pitfalls. Standards vary enormously, in terms of numbers of tests performed, experience of staff and exclusion criteria. Units collected differing amounts of sweat for different lengths of time and analysed different ions, reporting according to different reference material. Dr Kirk points out that in the US there is a well established quality assessment programme and a guideline document, Wales has its “Welsh sweat standard”, but the rest of the United Kingdom needs both local audit and national standardisation.

Also in this issue, Heeley and others from the East Anglia biochemical, genetic and neonatal screening unit report their comparisons of measuring sweat for sodium, chloride, osmolality and conductivity (page420). They investigated children with CF and controls, looking particularly at the overlap range, where results were regarded as diagnostically equivocal. It may surprise many readers to learn that conductivity was as effective as chloride in determining the presence of CF, while sodium and osmolality had wider overlaps.

Another variety of MSbP abuse

The March 2000 issue of our Fetal and Neonatal edition included a comprehensive seminar on hyperinsulinism. Not quite as comprehensive as we thought, it now appears. A group from Bristol, (page 392) report a 6 month old child with hypoglycaemic fits and hyperinsulinism who turned out to have been poisoned with an oral sulphonylurea, probably her grandmother's prescribed antidiabetic medication. This is another example of needing to keep Munchausen by proxy abuse in mind when faced with a bewildering clinical situation.

Smoke controls needed

Systematic reviews are useful not just in acute medicine. Drs DiGuiseppi and Higgins, from the Institute of Child Health in London, report their search for controlled trials evaluating interventions designed to increase usage of household smoke alarms (page 341). They conclude that counselling, as part of child health surveillance, may increase the likelihood that parents install and use an alarm. However, no RCT looked at whether injuries had been reduced as a result, although two non-randomised trials reported a reduction in fire related injuries. Media and community education had little benefit.

The authors recommend that future programmes promoting or supplying smoke alarms should be evaluated through properly designed RCTS measuring injury as an outcome.

harvey marcovitch Editor in Chief