Evaluation of the protein gap for detection of abnormal serum gammaglobulin level: an imperfect predictor
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Adam Suleman
,
D. William Cameron
Abstract
Objectives
The value of the serum protein gap (PG, difference between total protein and albumin) in the detection of hyper- or hypogammaglobulinemia is not well established. We assessed the performance of PG for the detection of hyper- or hypogammaglobulinemia in a large sample of patients.
Methods
We reviewed all paired measurements of serum total protein, albumin, quantitative immunoglobulins, and serum protein electrophoresis tested between March 2014 and June 2017 at the Eastern Ontario Regional Laboratory Association. Sensitivity, specificity, positive predictive value, negative predictive value and likelihood ratios of PG at thresholds between 18 and 44 g/L for the detection of hyper- and hypogammaglobulinemia were assessed.
Results
There were 19,575 and 5,426 simultaneous paired data points to assess hyper- and hypogammaglobulinemia identified by serum protein electrophoresis (SPE) and nephelometry, respectively. The mean PG was 36.3 g/L (SD 8.6). The prevalence of hypergammaglobulinemia (>16 g/L by SPE) and hypogammaglobulinemia (IgG <7 g/L) was 21.9 and 5.5%, respectively. High PG (≥38 g/L) had sensitivity and specificity of 76.2 and 71.5% respectively for hypergammaglobulinemia. PG ≥38 g/L had a negative predictive value (NPV) of 93.1% for monoclonal, and 96.9% for polyclonal gammopathy. A PG threshold of ≤18 g/L had of sensitivity of 0.4%, specificity of 100%, PPV of 100% and NPV of 80.1% to detect hypogammaglobulinemia (IgG <7 g/L).
Conclusions
High and low PG values were not sensitive in detecting hyper- or hypogammaglobulinemia, although negative predictive values were high for both. Performance of PG should be further evaluated prospectively in specific populations at risk of for abnormal IgG levels.
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Research funding: None declared.
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Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
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Competing interests: Authors state no conflict of interest.
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Informed consent: Informed consent was obtained from all individuals included in this study.
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Ethical approval: The study was approved by the Ottawa Hospital Research Institute Research Ethics Board (under the protocol number 20170437-01H).
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Supplementary Material
The online version of this article offers supplementary material (https://doi.org/10.1515/cclm-2020-1286).
© 2020 Walter de Gruyter GmbH, Berlin/Boston
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- Frontmatter
- Editorial
- Home pregnancy tests: quality first
- Review
- Non-invasive determination of uric acid in human saliva in the diagnosis of serious disorders
- Opinion Papers
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- The role of laboratory hematology between technology and professionalism: the paradigm of basophil counting
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- Evaluation of the ARKRAY HA-8190V instrument for HbA1c
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- Evaluation of dried blood spots as alternative sampling material for serological detection of anti-SARS-CoV-2 antibodies using established ELISAs
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