Letter to the Editor relating to Clin Chem Lab Med 2022;60(9):1365–72
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Xiang Sun
,
Qin Wang
To the Editor,
We read with great interest the article “Cross-reactivity in assays for prolactin and optimum screening policy for macroprolactinaemia” by Smith TP et al. [1]. However, we believe that the prevalence of macroprolactinaemia identified with an assay should not use the sera with hyperprolactinemia identified by another assay because of the circulating macroprolactin exhibiting molecular heterogeneity [2]. The composition of macroprolactin has been reported to be immunoglobulin G (IgG)-bound prolactin (PRL), anti-PRL autoantibody-bound PRL and other forms (non-IgG-bound PRL) [2, 3]. There is no consensus instruction indicating that the Tosoh assay could be used for identifying all cases of hyperprolactinemia due to macroprolactin. Interestingly, the authors only compared the 670 sera with hyperprolactinemia using a Tosoh immunoassay and did not include the remaining 2,431 sera with prolactin levels in the reference range using the same method. Therefore, we do not agree with the study design comparing the Roche assay and Tosoh assay using sera with hyperprolactinemia identified by Tosoh assay because they generated a bias regarding the sera. In fact, we found some important limitations stemming from the way the authors approached the selection of the sera. The statement of that the Roche immunoassay exhibited “low” reactivity toward macroprolactin may be estimated incorrectly for the mentioned reasons. Y Hu et al. showed that macroprolactinaemia was identified in 22.9% of 1,140 hyperprolactinemic patients screened with the Roche assay (Prolactin II) [4]. The prevalence of macroprolactinaemia is variable in different region [5]. Therefore, we kindly suggest that the authors perform an additional analysis on the prevalence of macroprolactinaemia using the Roche assay on unselected sera, which may come to the opposite conclusion. This sounds like a very interesting conclusion, but it is only speculative. The Roche immunoassay may exhibite “low” reactivity toward macroprolactin, using selected hyperprolactinaemic sera may lead false decreased evaluation, which is insufficiently strictly. We strongly recommend considering sample selection bias.
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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: Not applicable.
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Ethical approval: Not applicable.
References
1. Smith, TP, Kelly, S, Fahie-Wilson, MN. Cross-reactivity in assays for prolactin and optimum screening policy for macroprolactinaemia. Clin Chem Lab Med 2022;60:1365–72. https://doi.org/10.1515/cclm-2022-0459.Suche in Google Scholar PubMed
2. Nguyen, KQN, Langevin, RH, McPhaul, MJ, Hashim, IA. Circulating macroprolactin exhibits molecular heterogeneity and is not exclusively an antibody complex. Clin Chim Acta 2021;514:90–5. https://doi.org/10.1016/j.cca.2020.12.018.Suche in Google Scholar PubMed
3. Hattori, N, Ishihara, T, Saiki, Y, Shimatsu, A. Macroprolactinaemia in patients with hyperprolactinaemia: composition of macroprolactin and stability during long-term follow-up. Clin Endocrinol (Oxf). 2010;73:792–7. https://doi.org/10.1111/j.1365-2265.2010.03880.x.Suche in Google Scholar PubMed
4. Hu, Y, Ni, J, Zhang, B, Cheng, W, Zhang, H, Ye, H, et al.. Establishment of reference intervals of monomeric prolactin to identify macroprolactinemia in Chinese patients with increased total prolactin. BMC Endocr Disord 2021;21:197. https://doi.org/10.1186/s12902-021-00861-z.Suche in Google Scholar PubMed PubMed Central
5. Che Soh, NAA, Yaacob, NM, Omar, J, Mohammed Jelani, A, Shafii, N, Tuan Ismail, TS, et al.. Global prevalence of macroprolactinemia among patients with hyperprolactinemia: a systematic review and meta-analysis. Int J Environ Res Publ Health 2020;17:8199.10.3390/ijerph17218199Suche in Google Scholar PubMed PubMed Central
© 2022 the author(s), published by De Gruyter, Berlin/Boston
This work is licensed under the Creative Commons Attribution 4.0 International License.
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- Frontmatter
- Editorial
- Measuring FGF23 in clinical practice: dream or reality?
- Reviews
- Fibroblast growth factor 23: translating analytical improvement into clinical effectiveness for tertiary prevention in chronic kidney disease
- Pursuing appropriateness of laboratory tests: a 15-year experience in an academic medical institution
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- Analytical evaluation and bioclinical validation of new aldosterone and renin immunoassays
- Improving clinical performance of urine sediment analysis by implementation of intelligent verification criteria
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