["Corrected" calcium: calcium status underestimation in non-hypoalbuminemic patients and in hypercalcemic patients]. / Calcémie "corrigée": sous-estimation du statut calcique des patients sans hypoalbuminémie et des patients hypercalcémiques.

It is often reminded that if the ionized calcium is not measured, the interpretation of total calcemia should consider serum albumin. Two formulas are usually employed: ["Corrected" Ca (mmol/L) = Ca measured (mmol/L) + 0.020 or 0.025 (40 - albumin (g/L))]. This adjustment formula arises from works of Payne published in 1973. In a control population, we established the median values of calcium, albumin and ionized calcium (corrected to pH 7.40), respectively 2.34 mmol/L, 45.7 g/L and 1.23 mmol/L with our laboratory's methods (albumin - bromocresol green and Ca - ortho-cresolphtalein on a Modular analyser, Roche Diagnostics; ionized calcium with ion-selective electrode, Radiometer SA). Based on this, we retrospectively compared for 71 patients who do not belong to the control population the "corrected calcium" resulting from the two formulas and the measured calcemia to the ionized calcium corrected at pH 7,40. This comparison shows that in our laboratory, the two formulas lead to a rising underestimation of the calcium for albumin values greater than 40 g/L, reaching -0,20 mmol/L for albumin values above 44 g/L. The use of this formulas may also mask an hypercalcemia, indeed half of our patients' hypercalcemia (ionised Ca ((pH 7,40)) > 1,29 mmol/L) is not found. These results agree with Payne's recommendations for the use of his adjustment formula: the clinically justified adjustment of a low calcemia due to an hypoalbuminemia should not be extended to other situations, particularly when albumin is increased.

[Preanalytical variability of parathyroid hormone measurement in dialysis patients; application to Elecsys 2010 (Roche) automate]. / Variabilité préanalytique du dosage de la parathormone chez le patient dialysé; application à l'automate Elecsys 2010 (Roche).

The working group PTH-Vitamin D of the SFBC recently underlined the great intertechnic variability of parathormone (PTH) assays. At the same time, the data of the literature showed an impact of the preanalytic stage, significant and variable according to the automat used. We worked on the automat Roche Elecsys. On quickly centrifuged and decanted samples, the small difference in results between serum and plasma EDTA (6%) is compatible with an indifferent use of the two samples for dialysed patients. The reputation of greater stability on plasma EDTA seems primarily based on studies after decantation of plasma. The extension to a non decanted sample, maintained on primary tube for deferred shipping to the laboratory would require verification. Concerning the serum, on tube with serum separator, after early centrifugation, we checked the stability of the PTH measurement for a delay lower than or equal to 4 hours. For an extrahospital structure of dialysis, in the conditions of an early and an on site centrifugation, this delay allows to defer the transport of the primary closed tube to the laboratory. Contrary to plasma EDTA, the serum also allows simultaneous measurements of other parameters used for the care of the dialysed patients.

Inter-method variability in PTH measurement: implication for the care of CKD patients.

The National Kidney Foundation/Kidney-Dialysis Outcome Quality Initiative guidelines recommend to maintain the serum intact parathyroid hormone (PTH) concentration between 150 and 300 ng/l in chronic kidney disease (CKD) stage 5 patients. As these limits were derived from studies that used the Allegro intact PTH assay, we aimed to evaluate whether they were applicable to other PTH assays. We compared the PTH concentrations measured with 15 commercial immunoassays in 47 serum pools from dialysis patients, using the Allegro intact PTH assay as the reference. We also evaluated the recovery of graded amounts of synthetic 1-84 and 7-84 PTH added separately to a serum pool. Although the assays were highly correlated, the concentrations differed from one assay to another. The median bias between the tested assays and the Allegro intact PTH assay ranged from -44.9 to 123.0%. When the PTH concentrations were 150 or 300 ng/l with the Allegro intact PTH assay, they ranged with other assays from 83 to 323 ng/l and from 160 to 638 ng/l, respectively. The tested assays recognized 7-84 PTH with various cross-reactivities, whereas a given amount of 1-84 PTH was recovered differently by these assays. We found important inter-method variability in PTH results owing to both antibody specificity and standardization reasons. The unacceptable consequence is that opposite therapeutic attitudes may be reached in a single patient depending on the PTH assay used. We propose to use assay-specific decision limits for CKD patients, or to apply a correcting factor to the PTH results obtained with a given assay.

[Corneal precipitation of fluoroquinolones with magnesium]. / Cristallisation cornéenne de fluoroquinolones en présence de magnésium.

Infrared spectrophotometric analysis (FTIR) was performed on a crystalline deposit developed in a corneal ulcer by an old woman who received ciprofloxacine ophthalmic drops. We collected the data of the literature on the subject. After in vitro crystallization experiments, we conclude that ciprofloxacin and norfloxacin corneal precipitates occur at physiological lachrymal pH with magnesium.

[Comparison of methods for the determination of blood creatinine]. / Comparison des méthodes de dosage de la créatinine sérique.

Creatinine is the criterion the most widely used for kidney exploration, either directly or through algorithms. Up to now, it appears that methods of creatinine determination are still very heterogenous. The aim of the present study was to compare the different available methods and to evaluate their impact on the formula of predicted clearance. The study revealed that significant discrepancies can be observed depending on the methodology and analitycal principe. The results suggest that standardization of methods and comprehensive analysis of the different formula are necessary.

[Calcium-dependent calcium oxalate lithiasis (type IIa). The importance of urinary citrate and the calcium/citrate ratio]. / Lithiase oxalo-calcique de structure calcium dépendante (type IIa). Intérêt de la citraturie et du rapport calcium/citrate.

BACKGROUND: Type IIa urinary lithiasis (calcium oxalate dihydrate, weddellite) has a calcium-dependent structure implicating hyper-calciuria for its formation. CASE REPORT: We observed a case of type IIa lithiasis in a patient without elevated urine calcium. Weddellite crystals with a hexagonal habit were found in the nocturnal urines. The only urinalysis anomaly was a low citrate level giving a calcium/citrate level > 3. Oral potassium citrate normalized urinary citrate and the calcium/citrate ratio. After 3 years follow-up, crystal formation has remained negative. DISCUSSION: As illustrated by this case, the calcium/citrate ratio, rather than total urine calcium, would be a good indicator of urinary calcium output and the potential risk for weddellite crystal formation in the presence of oxalates.

[Calcium oxalate lithiasis. Relationship between biochemical risk factors and crystalline phase of the stone]. / Lithiase oxalocalcique. Relation entre facteurs de risque biochimiques et phase cristalline du calcul.

OBJECTIVES: To identify biochemical risk factors specific to each crystalline phase of calcium oxalate (calcium oxalate monohydrate and calcium oxalate dihydrate) in order to allow more specific medical management of calcium oxalate stones and better prevention of recurrences. MATERIAL AND METHODS: The authors compared the urine biochemistry (morning and 24-hour) of 19 patients with stones containing more than 95% of calcium oxalate monohydrate with those of 16 patients with stones containing more than 60% of calcium oxalate dihydrate (calcium phosphate < 12%). RESULTS: Urinary calcium, expressed as excretion rate and as concentration, and the calcium/citrate ratio were significantly higher in the calcium oxalate dihydrate group than in the calcium oxalate monohydrate group: (9.2 +/- 3.8 mmol/24 h versus 4.4 +/- 1.7 mmol/24 h); (4.9 +/- 2.1 mmol/l versus 2.4 +/- 1.1 mmol/l); (3.3 +/- 1.6 versus 1.6 +/- 0.7). The mean pH of the morning urine was lower in the calcium oxalate monohydrate group, just below the cut-off value of 5.5. CONCLUSION: There is a strong correlation between predominantly calcium oxalate dihydrate stones and hypercalciuria or calcium/citrate ratio > 3. The close relationship between urine biochemistry and crystalline phases of calcium oxalate confirms the clinical value of morphoconstitutional analysis of urinary stones. Identification of risk factors, based on stone analysis, allows more specific medical management of the stones and, in the longer term, better prevention of recurrences.

[Determination of Hb A1c in chronic renal failure. Contribution of new methodologies]. / Dosage de l'HbA1c chez l'insuffisant rénal chronique. Apports des nouvelles méthodologies.

Carbamylated haemoglobin arises from the non-enzymatic modification of haemoglobin by cyanate derived from spontaneous dissociation of urea. We studied the in vitro and in vivo interference of carbamylated haemoglobin in the assay of HbA1c by CLHP (ion exchange), affinity chromatography (IMX, Abbott) and immunoturbidimetry (Tina-Quant, Boehringer). For patients with chronic renal failure on continuous ambulatory peritoneal dialysis, CLHP assay of HbA1c gave an error of about +0.35% per 10 mmol/L of urea serum concentration. The IMX and especially Tina-Quant assays for measuring HbA1c were not sensitive to cyanate interference and constitute interesting alternatives for monitoring glycaemic balance in patients with chronic renal failure.

Effect of storage of samples at -80 degrees C on the assay of lipoprotein(a) by rate nephelometry (Beckman 360 Array).

The effect of storage of samples on the assay of lipoprotein(a) depends on the technique used. We have tested the automated Beckman 360 Array rate nephelometer using Dako anti-Lp(a) antibody, and an Immunofrance standard and control serum according to the technique of Gillery et al. We found a very high correlation between serum concentrations before freezing and those after three weeks and six months at -80 degrees C. Variations greater than 15% concerned only low levels of Lp(a) and were probably related to the precision of the technique at low concentrations.

Ambiguous patterns in cellular differentiation in a case of "M3 variant" leukemia.

We report a case of acute non lymphoblastic leukemia in which clinical and cytological patterns corresponded closely to the M3 variant as defined in the FAB classification, although we did not find the characteristic t (15; 17) chromosomal translocation. However, cytochemistry, DNA content studies and immunophenotyping showed unusual patterns suggesting a monocytic differentiation of most of the blast cells, while a smaller population of blasts showed in contrast typical markers of granulocytic lineage.