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The porphyrias are uncommon disorders of haem biosynthesis and their eVective management requires prompt and accurate diagnosis. This article describes methods for the determination of urinary porphobilinogen, urinary and faecal total porphyrins, and total porphyrins in erythrocytes and plasma that are suitable for use in non-specialist laboratories. The selection and interpretation of these methods, and the indications for further, more specialised, investigation are discussed. (J Clin Pathol 2001;54:500-507) Keywords: porphyria; haem biosynthesis; best practice guidelines Although the porphyrias are uncommon disorders of haem biosynthesis, the wide range and variability of their clinical features leads to their inclusion in the diVerential diagnosis of many diseases. Therefore, every acute hospital laboratory needs to have simple, reliable methods for their exclusion and for the identification of those few patients who need more specialised further investigation. Here, we describe methods that are suitable for the initial investigation of patients suspected of having porphyria. Accurate identification of the type of porphyria normally requires more sophisticated methods of analysis. These further investigations, family studies, and the investigation of asymptomatic patients with a past history of porphyria are best entrusted to specialised laboratories with expertise in the porphyrias. and are summarised in table 1. Each type results from partial deficiency of one of the enzymes of haem biosynthesis (fig 1). Accumulation of the substrate of the defective enzyme produces a pattern of accumulation and excess excretion of haem precursors and their derivatives that characterises each disorder (table 2). 3Symptoms that are caused by porphyria are always accompanied by detectable overproduction of haem precursors. Conversely, the absence of evidence for overproduction indicates that any concurrent symptoms are very unlikely to be the result of porphyria. Metabolite concentrations may be normal during remission and in all children and many adults who have inherited an acute porphyria but have never had symptoms (latent porphyria). In these circumstances, enzymatic or DNA analyses are required.

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Objective To assess the frequency of abnormal values for hormone measurements commonly used in the biochemical diagnosis of polycystic ovary syndrome (PCOS). Design Hormone measurements in 63 unselecled women with clinical and ultrasound diagnosis of PCOS attending gynaecological and general endocrine clinics in a District General Hospital were compared with those from a group of 20 normal ovula‐tory controls in the early follicular phase of their cycles. Measurements Serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), LH/FSH ratio, total testosterone, derived free testosterone, sex hormone binding globulin, androstenedione, and dehydroepiandrosterone (DHEA) were measured by radioimmunoassays. LH and FSH measured by two different assays. Results The mean serum LH and LH/FSH ratio were significantly (P<0.01) higher in the women with PCOS compared with the normal group, but these two measurements were in the abnormal range for only 35% and 41–44%, respectively. Absolute gonadotrophin values were significantly different using the two assay methods, which employed the same reference preparation as standard. Mean serum total testosterone concentration was significantly higher in the PCOS group and was the most frequently (70%) abnormal biochemical marker for PCOS. Sex hormone binding globulin (SHBG) did not differ significantly between the two groups but showed a negative correlation with body mass index in women with PCOS. The combination of SHBG and testosterone to derive a free testosterone value did not further aid the biochemical diagnosis of PCOS. Androstenedione was significantly higher in the PCOS group than in the control group, with a frequency of 53%. There was no significant difference in DHEA‐S between the two groups. Conclusion When typical ovarian ultrasound appearances plus the clinical features of oligomenorrhoea and/or hirsuitism were used to define PCOS total testosterone was the best single hormonal marker of the condition. Testosterone, androstenedione or LH, either alone or in combination, were raised in 86% of women with PCOS and these should be the definitive hormonal tests. Using LH/FSH ratio as a biochemical criterion for diagnosis of PCOS should be abandoned because of its low sensitivity. To be of value the normal range for all hormones should be precisely defined in a group of regularly ovulating women in the early follicular phase of the cycle for the assay used in each laboratory.

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