Post-reperfusion inflammation as well as anti-allograft response occur following kidney transplantation. We evaluated tissue damage by multiple renal indicators and searched for rejection predictors forewarning serum creatinine upturns. Twenty recipients (43 +/- 9 y; donors' age 35 +/- 16 y) of first renal grafts were studied. All through their hospital stay (35 +/- 18 d, range 17-75 d) we measured serum levels of urea, creatinine and electrolytes along with urinary excretion rates of total protein, albumin, enzymes (GGT, NAG, AAP) and electrolytes. During the period of observation, peaks were seen on the 1st day for serum creatinine, serum K+ and urine albumin output; on the 2nd day for urine Na+, GGT, AAP and protein excretion rates; on the 4th day for urea and creatinine outputs; on the 5th day for NAG output. On the 14th day, serum urea and creatinine as well as urine GGT, NAG, AAP, albumin and total protein were still elevated compared to 20 healthy control subjects. Delayed/slow graft function was observed in six recipients with higher pre-transplantation plasma lipids and lower donor HDL cholesterol. Hospital stay time was correlated with need for post-transplantation dialysis (p = 0.01) and recipient proteinuria by time 0 (TO) to day 3 (p = 0.02). Cold ischemia time was positively associated with 0-3 d serum creatinine, 0-3 d urinary urea and protein outputs (multiple r 0.9, p < 0.001). Multivariate analysis of longitudinal data showed that recipients' serum creatinine was positively correlated (p < 0.001) with urine AAP and negatively correlated with urine albumin, with diuresis volume and urine creatinine (p < 0.01). Serum creatinine elevations were preceded (previous 1-7 d) by increases in urinary indicators, the probability being higher in the presence of multiple simultaneous abnormalities. Useful parameters predictive of favorable graft outcome prior to transplantation included a brief cold ischemia time and a normal donor/recipient serum lipoprotein profile. Following transplantation, useful parameters were a high diuresis volume at time zero along with low urine NAG and high albumin outputs; early (first opst-graft 3 d) polyuria, low urea and GGT, high K, NAG and total protein excretions.
Measurement of the urinary albumin excretion rate (UAER) is essential for the early diagnosis and monitoring of diabetic nephropathy; immunonephelometry is a procedure used worldwide for routine screening of diabetic patients. Since we have met with occasional inconsistent values of UAER in serial urine collections, we searched for possible sources of analytic error. To assess the best working conditions of the instrument in use, the stability of urine samples during storage and the need for previous urine centrifugation, we assayed repeatedly the six automatically diluted points of the standard curve (55.6 to 1.7 mg/l), four control samples of human albumin in saline (100 to 1 mg/l) and 24-h urine collections from outpatient diabetic subjects. The last were also assayed with and without previous centrifugation, and both immediately after collection as well as after storage at -20 degrees C for 7, 42, 79, 97, 128 and 161 days. We concluded that: (1) pre-analytic centrifugation of urine samples in unnecessary; (2) the intra-assay coefficient of variation (CV) of the standard curve changed from 2.4% to 9.3% when moving from the highest to the lowest concentration; the inter-assay CV changed from 4.1% to 14.4%, respectively; (3) the intra-assay CV of the control samples (manually prepared) changed from 5.7% to 10.2% and the inter-assay CV from 7.7% to 22.9%; there was a constant and significant (P < 0.01) underestimation (from -9% to -30%) of the obtained values compared with the expected concentrations; (4) a progressive decrease in recovered albumin by multiple freezing and thawing of urine samples did occur, which became significant after 161 days of storage. In the BNA workbook (menu 7.1, assay protocols), a 7-day validity of the reference curve is reported. Moreover, to economize, pre-dilution cuvettes were often recycled in our hospital central laboratory. We observed that: the intra-assay CV for urine samples was 79.4% with recycled cuvettes and stored standard curve, 11.3% with new cuvettes and stored standard curve, 4.9% with both new cuvettes and newly performed standard curve; the inter-assay CV was 32.6%, 10.5% and 6.4%, respectively. These data emphasize, from the laboratory viewpoint, the need for both accurate calibration of BNA and use of native urines; in addition, they stress the importance of careful supervision of laboratory routine and interpreting analytic results in the clinical setting.
The clinical usefulness of glycated hemoglobin (HbA1C) depends crucially on the accuracy and precision of its assay. When we compared an immunological bench-top analyzer (DCA 2000, Bayer Diagnostici, Milan) to the high-performance liquid chromatography (HPLC) reference method used in a routine hospital laboratory (Diamat and Fast Diamat, Bio-Rad Lab., Milan) by assaying multiple control sera, we found so many sources of systematic analytical errors in the routine use of HPLC as to compromise between-assay precision. DCA 2000 showed intra- and interassay coefficients of variation (CV) of 1.1% and 2.3% with the normal standard serum, 1.0% and 4.2% with the pathological one; Diamat yielded CVs of 1.3% and 7.0%, 1.3% and 5.7%, respectively. Although the measurement of 161 blood samples showed that Diamat usually overestimated HbA1C (paired t-test, P<0.001), a great variability of Diamat performance became evident when the relationship Diamat vs DCA was evaluated day by day over 17 days of observation (analysis of variance, ANOVA, P<0.001). Intra- and interassay CVs of Fast Diamat initially (new instrument still on approval) were 0.6% and 2.5% (normal standard serum), 0.3% and 1.9% (high standard serum), yet after 6 months of routine laboratory use, they became 3.1% and 3.2%, 1% and 12.3%, respectively. Main sources of error were: inaccurate autodilution, unsuitable parameter settings, disregard of the maintenance schedule. We conclude that the tendency to overlook major critical aspects in the routine use of HPLC is detrimental to the quality of HbA1C determination and implies the loss of HbA1C value in clinical practice. Both carefully supervising laboratory quality and checking the likelihood of the analytical result with the clinical setting appear even more important.
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