Dario Mandić

Falsely elevated serum oestradiol due to exemestane therapy

In this study, we present a case of falsely elevated oestradiol (E2) concentration, determined by two immunoassays, in a breast cancer patient receiving exemestane therapy. The positive bias of immunochemical measurements was revealed using liquid chromatography tandem mass spectrometry which showed undetectable E2 concentration. The discrepancy is expected to be a consequence of the structural resemblance of E2 and exemestane sharing the same steroidal backbone. Inaccurate laboratory findings in therapy monitoring, as in this case, may lead to unnecessary changes of therapy.

Differentiation of acute pyelonephritis from other febrile states in children using urinary neutrophil gelatinase-associated lipocalin (uNGAL)

Abstract Background: Acute pyelonephritis is a severe disease which is sometimes difficult to recognize based on clinical symptoms and routinely available diagnostic tests, especially in young children. The aim of this study was to assess the diagnostic value of urinary neutrophil gelatinase-associated lipocalin (uNGAL) as a biomarker of acute pyelonephritis. Methods: In this case-control study we analyzed 134 children (median age 2.5 years) who were admitted to the Pediatric Clinic of University Hospital Centre Osijek, Croatia. Eighty of them had acute pyelonephritis, while 54 children had febrile state of different etiology including cystitis and they represented the control group. uNGAL, white blood cells, C-reactive protein, urinanalysis, urine culture, kidney ultrasound and a dimercaptosuccinic acid scintigraphic scan were done for each child. uNGAL was measured using chemiluminiscent microparticle immunoassay on ARHITECT i1000SR (Abbott Diagnostics, IL, USA). Results: uNGAL values were significantly higher in children with acute pyelonephritis compared to the control groups (113.6 ng/mL vs. 10.2 ng/mL, p<0.001). A receiver operating characteristic curve comparison was done for tested parameters and encouraging results were obtained for uNGAL (AUC=0.952). A cut-off value of 29.4 ng/mL had 92.5% sensitivity and 90.7% specificity. We showed that uNGAL can also serve in differentiating acute pyelonephritis from cystitis (cut-off 38.5 ng/mL), and for differentiation of cystitis from febrile states with etiology other than urinary tract infection (UTI) (cut-off 20.4 ng/mL). Conclusions: uNGAL can be a useful diagnostic biomarker in acute pyelonephritis in children, but also in differentiating cystitis from febrile states other than UTI.

INFLUENCE OF EXTRACTION TECHNIQUES ON GC-MS SCREENING RESULTS

Gas chromatography coupled with mass spectrometry (GC-MS) is often used as a confirmatory technique for positive results obtained with immunoassay screening tests, but it can also be used as a screening method in clinical and forensic toxicology. Because of different reasons (amount of sample available, urgency, cost of analysis, etc.), laboratory is often in position to perform just one extraction and screening per sample. Influence of different extraction procedures on results is usually overlooked, but it can have great impact on obtained results, both quantitatively and qualitatively. We prepared four different levels of commercial urine toxicology control samples Liquichek (BIO-RAD), containing 12 drugs-ofabuse using three different extraction procedures: liquid– liquid extraction system TOXI-TUBES A (VARIAN), liquid–liquid extraction system Chem Elut (VARIAN) and solid phase extraction system based on Amberlite XAD2 polymeric adsorbent columns (Sigma–Aldrich). All extracts were analyzed with GC-MS (SHIMADZU GCMS-QP5050A). Obtained results are presented and influence of extraction procedure on GC-MS screening results is evaluated for every extraction procedure.