Melaminium 2,4,6-trihydroxy-benzoate dihydrate.

In the title compound, C(3)H(7)N(6) (+)·C(7)H(5)O(5) (-)·2H(2)O, the melaminium and benzoate ions are approximately planar (r.m.s. deviation of the non-hydrogen atoms is 0.093 Å) and there is a strong C(2) (2)(8) hydrogen-bonding embrace between them. The centre of symmetry generates a second acid-base pair which is bound to the first by a C(2) (2)(8) (N-H⋯N) embrace common between melamine mol-ecules in similar compounds. Further extensive hydrogen bonding assembles the components into a three-dimensional hydrogen-bonded network.

The effect of storage conditions on sample stability in the routine clinical laboratory.

BACKGROUND: 'Add-on' tests are often requested for samples already in the laboratory. This study was carried out to assess the stability of common analytes in uncapped samples stored in different conditions, and therefore their suitability for 'add-on' requests. METHODS: Storage conditions evaluated included initial storage at room temperature for 16 hours, followed by storage at 4℃ (Group 1: current conditions employed in the laboratory), compared with storage at 4℃ immediately following analysis (Group 2: optimum storage conditions). RESULTS: Some analytes were not suitable for 'add-ons' when samples were stored in either storage condition, whereas some were suitable for 'add-ons' irrespective of storage condition. Storage conditions influenced the suitability of 'add-on' tests for a proportion of analytes including urea, amylase, total protein, alkaline phosphatase, adjusted calcium, lactate dehydrogenase, triglycerides, HDL cholesterol and total cholesterol; these analytes were stable in optimum conditions (Group 2) but not in current conditions (Group 1). CONCLUSIONS: 'Add-on' tests can only be safely performed on a proportion of routine analytes. For some analytes, storage conditions affect their suitability for delayed analysis.

A comparison of the analytical performance of five commercially available assays for neutrophil gelatinase-associated lipocalin using urine.

BACKGROUND: Neutrophil gelatinase-associated lipocalin (NGAL) is a promising biomarker for acute kidney injury that is beginning to be used in clinical practice in addition to research studies. The current study describes an independent validation and comparison of five commercially available NGAL assays, focusing on urine samples. This is an essential step in the translation of this marker to clinical use in terms of allowing valid inter-study comparison and generation of robust results. METHODS: Two CE (Conformité Européenne)-marked assays, the NGAL Test (BioPorto) on Siemens ADVIA(®) 1800 and the ARCHITECT Urine NGAL assay on i2000SR (Abbott Laboratories), and three research-use-only (RUO) ELISAs (R&D Systems, Hycult and BioPorto) were evaluated. Imprecision, parallelism, recovery, selectivity, limit of quantitation (LOQ), vulnerability to interference and hook effect were assessed and inter-assay agreement was determined using 68 urine samples from patients with various renal diseases and healthy controls. RESULTS: The Abbott and R&D Systems assays demonstrated satisfactory performance for all parameters tested. However for the other three assays evaluated, problems were identified with LOQ (BioPorto/ADVIA(®)), parallelism (BioPorto ELISA) or several parameters (Hycult). Between-method agreement varied with the Hycult assay in particular being markedly different and highlighting issues with standardization and form of NGAL measured. CONCLUSIONS: Variability exists between the five NGAL assays in terms of their performance and this should be taken into account when interpreting results from the various clinical or research studies measuring urinary NGAL.