Characteristics of Monoclonal Immunoglobulins That Interfere with Serum Inorganic Phosphate Measurement

Bowles, Shirley A; Tait, Robert C.; Jefferson, Stephen G; Gilleece, Maria; Haeney, M R

doi:10.1177/000456329403100306

Cited by 25 publications

(8 citation statements)

References 9 publications

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“…In previous reports where a series of patient samples was investigated, different criteria for pseudohyperphosphataemia were used, 6,9,11,12 and this may explain the variable incidence (8-49%) of this phenomenon.…”

Section: Discussionmentioning

confidence: 99%

Paraprotein Interference Causing Pseudohyperphosphataemia: Evaluation of an Improved Methodology

Savory

Pearce

1995

Ann Clin Biochem

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SUMMARY. The measurement of serum inorganic phosphorus by direct acidl molybdate assay is known to be subject to interference by some serum paraproteins. Serum samples from 45 paraproteinaemic patients were used for the measurement of inorganic phosphorus using a manufacturer's kit reagent and a detergent-modified reagent from the same manufacturer. In addition, the same samples were analysed with both reagents following precipitation of serum protein with trichloroacetic acid. Using the original reagent pseudohyperphosphataemia was found in 27ftJo (12/45) of the samples. The modified reagent was free from interference with no significant difference between results from serum and protein-free supernatants. Additional key phrases: acid molybdate inorganic phosphorusPseudohyperphosphataemia has been reported previously in patients with paraproteins. Some studies have shown that interference is due to turbidity caused by precipitation of the paraprotein by the acid reagent used in both visible and ultra-violet spectrophotometric methods.l:'! Other workers have identified the presence of a phosphate binding immunoglobulin.P:"! The Boehringer Mannheim (BM UK Ltd, Sussex, UK) method for inorganic phosphorus (Product No. 1040898) is known to be subject to interference in some patients with paraproteins." The manufacturer's claim that interference has been reduced significantly by a recent change in reagent composition.We have compared the performance of the two reagent kits in samples from 45 patients with paraproteinaemia using whole serum and proteinfree supernatants of the same serum. MATERIALS AND METHODSBlood samples from 45 patients in whom paraproteins had previously been identified by electrophoresis and typing by immunofixation were obtained for diagnosis or treatment monitoring.Correspondence: D J Savory. 498The study included samples with IgG (n = 36, range 8-80 giL), IgA (n = 5, range 11-28 giL) and IgM (n = 4, range 10-33 giL) paraproteins. Aliquots of serum were stored at -20°C prior to analysis.Serum inorganic phosphorus was measured on an Hitachi 717 using two kits (BM Cat No. 1040898) of different lot numbers. Kit X (Lot No. 645386) was the original formulation, and Kit Y (Lot No. 650415) contained the modified reagent. Serum was diluted with sulphuric acid and the blank absorbance measured at 340 nm and 376 nm. On addition of ammonium molybdate, inorganic phosphorus is converted to ammonium phosphomolybdate which is measured at 340 and 376 nm. The final concentrations were: molybdate 1·0 mmol/L, sulphuric acid 0·35 mol/L, sodium chloride 44 mmol/L and detergent. Kits X and Y differed in detergent composition, the details of which have not been disclosed by the manufacturers.The same serum samples were analysed using both reagents after precipitation of protein using equal volumes of serum and 0·61 mol/L trichloracetic acid, the method currently in use in this laboratory when hyperphosphataemia is found in patients with paraproteins. The supernatant was analysed directly following centrifugation.Inorg...

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Section: Discussionmentioning

confidence: 99%

Paraprotein Interference Causing Pseudohyperphosphataemia: Evaluation of an Improved Methodology

Savory

Pearce

1995

Ann Clin Biochem

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“…The testing for up to half of patients with monoclonal immunoglobulinemia showed interference in phosphate assay. 19 Large reviews of patients with paraproteinemia show that the immunoglobulin concentration in patients with factitious results did not differ from patients without the interference. 19 When the interference occurred, however, the degree of interference was proportional to the immunoglobulin levels.…”

Section: Paraproteins and Polyclonal Hyperimmunoglobulinemiasmentioning

confidence: 99%

“…The opaque precipitates interfere with automated nephelometric, turbidimetric, colorimetric, and light-scatterbased autoanalyzers. 6,11,16,[19][20][21][22][23][24]35,39,85 (2) Immunoglobulins may chemically inactivate the test reagents. (3) Immunoglobulins increase the colloid phase of plasma and relatively decrease the aqueous phase, thereby reducing the amount of water-soluble molecules.…”

Section: Paraproteins and Polyclonal Hyperimmunoglobulinemiasmentioning

confidence: 99%

Factitious Biochemical Measurements Resulting From Hematologic Conditions

Dalal

Brigden

2009

American Journal of Clinical Pathology

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Factitious laboratory results often lead to unnecessary testing or treatment. This brief review of factitious biochemical results due to preexisting hematologic conditions focuses on the mechanisms underlying the factitious results and suggests ways to prevent them. An observant pathologist identifies these errors, intervenes in a timely fashion, investigates the sources of error diligently, and institutes measures to prevent their recurrence.

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“…The immunoglobulins in these samples tend to form precipitates that may cause significant light scattering during spectroscopic analysis, resulting in erroneous laboratory results. The extent of this interference is not easily predictable and bears no relationship to the type, concentration or physicochemical properties of the immunoglobulin (5). The extent of this interference is not easily predictable and bears no relationship to the type, concentration or physicochemical properties of the immunoglobulin (5).…”

Section: Introductionmentioning

confidence: 99%

“…Several authors have recognized the problems involved in the analysis of blood or sera from patients with hypergammaglobulinemia (1)(2)(3)(4)(5). The immunoglobulins in these samples tend to form precipitates that may cause significant light scattering during spectroscopic analysis, resulting in erroneous laboratory results.…”

Section: Introductionmentioning

confidence: 99%

Study of IgM Aggregation in Serum of Patients with Macroglobulinemia

Sharma¹,

Baker

Brooks

et al. 2000

CCLM

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The effect of solvent conditions on the aggregation of IgM in serum specimens from patients with macroglobulinemia was studied by a turbidimetric procedure. Aggregation of IgM varied considerably among the samples and was affected by a number of experimental parameters. In general, IgM aggregation was more pronounced under acidic conditions and in solvents with low ionic strength. The presence of water-miscible organic solvents also promoted aggregation. Based on these studies, it was concluded that the major force involved in the formation of immunoglobulin aggregates in the serum of patients with macroglobulinemia was electrostatic, rather than hydrophobic, interactions. A number of additives known to prevent protein aggregation were evaluated for their effectiveness in inhibiting IgM aggregation. The only additives that were shown to inhibit or reduce IgM aggregation were charged molecules, such as arginine, sodium chloride, ethylenediamintetraacetic acid and quaternary ammonium beta-cyclodextrin. Some of these charged additives were also effective in dissociating the IgM aggregates once they were formed, even in the presence of detergent.

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Characteristics of Monoclonal Immunoglobulins That Interfere with Serum Inorganic Phosphate Measurement

Cited by 25 publications

References 9 publications

Paraprotein Interference Causing Pseudohyperphosphataemia: Evaluation of an Improved Methodology

Paraprotein Interference Causing Pseudohyperphosphataemia: Evaluation of an Improved Methodology

Factitious Biochemical Measurements Resulting From Hematologic Conditions

Study of IgM Aggregation in Serum of Patients with Macroglobulinemia

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