Comparison of Two Methods for Determination of NGAL Levels in Urine: ELISA and CMIA.

BACKGROUND: Neutrophil gelatinase-associated lipocalin (NGAL) is a new useful biomarker for the early diagnosis of acute kidney injury. The aim of the study was to compare two analytical methods for measurement of urinary NGAL: enzyme-linked immunosorbent assay (ELISA) and chemiluminescent microparticle immunoassay (CMIA). METHODS: Two assays were used to measure urinary NGAL: ELISA kit (R&D Systems) and ARCHITECT Urine NGAL (Abbott Laboratories). The study material was the urine obtained from 30 healthy subjects (mean age 56.4 ± 15.2). RESULTS: The median value and interquantile range of urinary NGAL in the studied group measured by ELISA (R&D Systems) were 3.5 ng/ml (1.2; 6.6) and by CMIA (ARCHITECT Urine NGAL assay, Abbott Diagnostics) were 4.4 ng/ml (1.9; 9.4). Levels of urinary NGAL obtained by CMIA were significantly higher than by ELISA. There was a significant positive correlation between the concentration of urinary NGAL determined by both methods (r = 0.8625, P < 0.01). CONCLUSION: The comparison of individual data obtained by ELISA and CMIA should be taken with care. From laboratory's point of view, ELISA is less expensive than CMIA method for the determination of NGAL in urine. However, CMIA method allows rapid determination of urinary NGAL concentration through automated assay.

Effect of nitrous oxide on cerebral blood flow in normal humans.

We have studied the effect of nitrous oxide on cerebral haemodynamics in 24 healthy male volunteers. Hemispherical cerebral blood flow (CBF) was measured using the xenon-133 inhalation technique, blood flow velocities in the right middle cerebral artery were calculated using transcranial Doppler ultrasound and the pulsatility index (PI)--the inverse of which is theoretically proportional to flow in the vessel under investigation--was derived from analysis of the spectrally analysed velocity pulse wave form obtained from the middle cerebral artery. Each variable was measured with the subject inhaling 100% oxygen (1st baseline), 30% nitrous oxide in oxygen, 100% oxygen (2nd baseline) and 60% nitrous oxide in oxygen. CBF was significantly greater with 30% (0.01 > P > 0.001) and 60% nitrous oxide (P < 0.001) compared with baseline, although the difference between 30% and 60% nitrous oxide was not significant. Changes in 1/PI correlated closely with those in hemispherical CBF. Blood flow velocities increased significantly with 30% (P < 0.001) and 60% nitrous oxide (0.005 > P > 0.001), the difference between 30% and 60% nitrous oxide also being significant (0.005 > P > 0.001). We observed a plateau in the change in CBF caused by nitrous oxide and suggest that this may be explained by activation of intact autoregulative mechanisms in healthy human brain.

Treatment of toxic epidermal necrolysis and a review of six cases.

Six cases of drug-induced toxic epidermal necrolysis treated in a burns unit are presented. The mean skin loss was 67.3 per cent of the total body surface area. Two patients developed renal failure and two had ocular symptoms. The mortality rate was 50 per cent, with two patients dying from septicaemia and one from respiratory and renal failure. The diagnosis of toxic epidermal necrolysis can be confirmed by skin biopsy. We recommend that this disease is treated in a burns unit so that both adequate wound care and essential intensive supportive treatment can be given. Antibiotics are indicated only for specific infections such as septicaemia or pneumonia. Steroids have been shown to increase greatly the mortality from septic complications and are not recommended. The mortality ranges from 10 per cent to 70 per cent and bad prognostic factors include increasing age, greater than 50 per cent of body surface skin loss and neutropenia.

Characterization of peptides found in human biological fluids in macroglobulinemia IgM.

Excessive production of IgM in macroglobulinemia is accompanied frequently by secretion of proteins and peptides which are normally absent from biological fluids. These proteins and peptides are probably secreted by cells producing IgM. Three types of peptides were isolated and their basic properties are described. One peptide showed calcium-binding properties, and the other two peptides were bound to secreted IgM immunoglobulin.

Some properties of a glycoprotein with calcium binding ability found in human biological fluids in macroglobulinaemia IgM.

An acidic glycoprotein with calcium-binding properties was isolated from the urine of patients with severe macroglobulinaemia IgM. The molecular weight of this protein determined by Sephadex gel filtration was found to be 62 000 +/- 2800 in Tris - HCl buffer and 21 000 +/- 1000 in 6 M guanidine - HCl. The amino acid and carbohydrate composition of the isolated glycoprotein is presented. Electrophoretic migration of this protein was observed to be greatly affected by calcium ions present in the buffer in a concentration of 10(-3) M. At least two sets of binding sites seem to participate in binding calcium. The values 2.2 - 10(6) M-1 for the apparent association constant and 4.4 - 10(-4) mol of Ca2+ bound per g of protein for high affinity bindings sites were estimated, on the basis of data from the equilibrium dialysis. The origin and possible biological role of this protein is discussed.