Laboratory investigation in the diagnosis of pulmonary thromboembolism.

Laboratory findings were compared with lung scans in a prospective study of 260 patients undergoing ventilation-perfusion (V/Q) lung scanning for suspected pulmonary thromboembolism. The best discrimination between different lung scan results was obtained from the level of plasma cross-linked fibrin degradation products, every patient with a scan indicating a high probability of thromboembolism having detectable levels. An acute phase response was demonstrated in patients with pulmonary thromboembolism by a raised neutrophil count and elevated levels of plasma fibrinogen and serum C-reactive protein. A normal level of serum C-reactive protein and/or plasma cross-linked fibrin degradation productions in blood taken within 4 days of onset of symptoms virtually excluded the diagnosis of pulmonary thromboembolism. Detection of free plasma DNA was not helpful in discriminating between groups with different lung scan results. Discriminant analysis was used to assess the variables examined and to derive diagnostic models. An accuracy of 78 per cent was obtained with one model for classifying test patients according to the three lung scan classes of low, intermediate and high probability. A second model, for distinguishing patients with a low and a high probability of pulmonary thromboembolism on the basis of lung scans, and a third for predicting those with a low probability on lung scan, were accurate in 94.6 per cent and 83.5 per cent of patients respectively. Discriminant models could be used in the diagnosis of pulmonary thromboembolism, especially when diagnostic imaging is not available.

How useful is riboflavin as a tracer of medication compliance?

A quantitative spectrofluorometer assay of urinary riboflavin is described. Using the method, levels produced by prescribed riboflavin are reliably distinguished from normal background levels without requiring dietary restrictions. The method is successfully used to verify the intake of a single 50-mg dose of riboflavin. However, when more frequent dosage is used, verification becomes unreliable because of a "spillover" effect produced by the slow rate of elimination of the substance. This seriously limits the utility of riboflavin as a tracer, as does its tendency to change the appearance of therapeutic compounds into which it is incorporated. The need for further work on validating combined measures of compliance is stressed.

Prenatal diagnosis of disorders of galactose metabolism.

Of three clinically significant galactose disorders, there is only a real need and experience of prenatal diagnosis in classical galactosaemia. Prenatal diagnosis for this disorder may be carried out by galactose-1-phosphate uridyl transferase assay in cultured amniotic fluid cells or in chorionic villus biopsies and by galactitol estimation in amniotic fluid supernatant. Although the long-term outcome of patients treated on a galactose-restricted diet is recognized to be unsatisfactory, prenatal diagnosis is only rarely performed with a view to terminating the affected pregnancy.

Galactosaemia: a new severe variant due to uridine diphosphate galactose-4-epimerase deficiency.

A baby presented on day 5 with symptoms of classical galactosaemia which are believed to be owing to a lack of uridine diphosphate-4-epimerase, rather than to the usual galactose-1-phosphate uridyl transferase defect. Apart from galactosaemia the condition was characterised biochemically by a red cell accumulation of galactose-1-phosphate and uridine diphosphate galactose. Galactose restriction modified the acute clinical and biochemical abnormality, but it appears essential to include some galactose in the diet in this condition to allow synthesis of galactosides, including the brain gangliosides.

Gas-liquid chromatographic determination of galactitol in amniotic fluid for possible use in prenatal diagnosis of galactosaemia.

A gas liquid chromatographic method for the estimation of galactitol in amniotic fluid from pregnancies at risk for galactosaemia is described. The method is based on the almost complete removal of glucose from the amniotic fluid by ion exchange, and the subsequent chromatography of galactitol as its hexaacetate.