A nucleic acid amplification procedure, the polymerase chain reaction (PCR), has been used to establish a diagnostic assay for the identification of cytomegalovirus (CMV) immediateearly sequences in clinical specimens. Preliminary testing against virus-infected cell cultures indicated that the PCR assay was highly CMV-specific, recognizing both wild-type and laboratory strains of CMV. There was no cross-reactivity with human DNA or with DNA from other herpes viruses. The sensitivity of the assay, using cloned CMV AD169 Eco RI fragment-J as template, was 1 viral genome per 40,000 cells. In a prospective study of CMV infection in bone marrow transplant recipients, the PCR assay correctly identified four patients with confirmed CMV infection. In three of these patients who were followed longitudinally, correlation of DNA reactivity with CMV culture and CMV antibody status over time indicated that DNA was the most sensitive marker for the diagnosis of CMV infection.

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Although the active pharmaceutical ingredient remains constant, the excipients used will vary according to the manufacturer. This case report is of spuriously raised serum creatinine due to an excipient in one particular intravenous dexamethasone formulation. A patient had three serum creatinine measurements of 102, 369 and 91 mmol/L over a four-hour period. The second result was believed to be spurious and appropriate investigations were instigated. The patient had received dexamethasone intravenously between the first and second blood samples. This was administered as a bolus via a cannula in the dorsum of the hand, and the blood sample was taken by venepuncture of the antecubital fossa of the same arm approximately five minutes later. The dexamethasone used (Hospira UK Ltd) contained creatinine at a concentration of 70,720 mmol/L, with a total of 170 mmol of creatinine given to the patient. Assuming a volume of distribution of 40 L in a 70-kg man, an increase in serum creatinine of 4 -5 mmol/L would be expected once equilibrated. It is thought that the serum creatinine result observed was a consequence of the creatinine excipient in the dexamethasone not having completely distributed throughout the body and still being at relatively high concentrations within the limb into which it had been administered. Intravenous dexamethasone can lead to spurious creatinine results, not due to analytical interference but rather the analytically correct measurement of creatinine added as an excipient. This case clearly demonstrates the impact preanalytical factors can have on the accuracy of results.

SUMMARY. A traditional electrophoretic procedure for detection of Bence-Jones proteinuria, employing Amido black stain on 200-fold concentrated urine, has been compared to two procedures employing highly sensitive protein stains not requiring prior urine concentration. All three procedures were carried out on 80 random urine samples screened for Bence-Jones proteinuria and 10 samples were provided by patients attending a myeloma clinic. A new procedure employing modified Coomassie brilliant blue stain on unconcentrated urine showed comparable sensitivity to the established procedure (82% versus 88%, respectively) and specificity (77% versus 74%, respectively), when assessed against immunofixation as a reference method. However, the new method is considerably quicker and cheaper. A second method, employing Gold stain, showed enhanced sensitivity (94% versus 88% for Amido black) but lower specificity (62% versus 74% for Amido black). However, this method is labour intensive and relatively expensive. Our data suggest that the procedure employing modified Coomassie brilliant blue may be a suitable alternative to the traditional procedure commonly used in many clinical laboratories.