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Marques-Garcia F, Boned B, González-Lao E, Braga F, Carobene A, Coskun A, Díaz-Garzón J, Fernández-Calle P, Perich MC, Simon M, Jonker N, Aslan B, Bartlett WA, Sandberg S, Aarsand AK. Critical review and meta-analysis of biological variation estimates for tumor markers. Clin Chem Lab Med 2022; 60:494-504. [PMID: 35143717 DOI: 10.1515/cclm-2021-0725] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 02/01/2022] [Indexed: 01/21/2023]
Abstract
OBJECTIVES Biological variation data (BV) can be used for different applications, but this depends on the availability of robust and relevant BV data. In this study, we aimed to summarize and appraise BV studies for tumor markers, to examine the influence of study population characteristics and concentrations on BV estimates and to discuss the applicability of BV data for tumor markers in clinical practice. METHODS Studies reporting BV data for tumor markers related to gastrointestinal, prostate, breast, ovarian, haematological, lung, and dermatological cancers were identified by a systematic literature search. Relevant studies were evaluated by the Biological Variation Data Critical Appraisal Checklist (BIVAC) and meta-analyses were performed for BIVAC compliant studies to deliver global estimates of within-subject (CVI) and between-subject (CVG) BV with 95% CI. RESULTS The systematic review identified 49 studies delivering results for 22 tumor markers; four papers received BIVAC grade A, 3 B, 27 C and 15 D. Out of these, 29 CVI and 29 CVG estimates met the criteria to be included in the meta-analysis. Robust data are lacking to conclude on the relationship between BV and different disease states and tumor marker concentrations. CONCLUSIONS This review identifies a lack of high-quality BV studies for many tumor markers and a need for delivery of BIVAC compliant studies, including in different, disease states and tumor marker concentrations. As of yet, the state-of-the-art may still be the most appropriate model to establish analytical performance specifications for the majority of tumor markers.
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Affiliation(s)
- Fernando Marques-Garcia
- Biochemistry Department, Metropolitan North Clinical Laboratory (LCMN), Germans Trias i Pujol Universitary Hospital, Badalona, Barcelona, Spain.,Spanish Society of Laboratory Medicine (SEQCML), Analytical Quality Commission, Barcelona, Spain
| | - Beatriz Boned
- Spanish Society of Laboratory Medicine (SEQCML), Analytical Quality Commission, Barcelona, Spain.,Royo Villanova Hospital, Zaragoza, Spain
| | - Elisabet González-Lao
- Spanish Society of Laboratory Medicine (SEQCML), Analytical Quality Commission, Barcelona, Spain.,Quality Healthcare Consulting, Grupo ACMS, Barcelona, Spain
| | - Federica Braga
- Research Centre for Metrological Traceability in Laboratory Medicine (CIRME), University of Milan, Milan, Italy
| | - Anna Carobene
- Servizio Medicina di Laboratorio, Ospedale San Raffaele, Milan, Italy
| | - Abdurrahman Coskun
- School of Medicine, Acibadem Mehmet Ali Aydınlar University, Atasehir, Istanbul, Turkey
| | - Jorge Díaz-Garzón
- Spanish Society of Laboratory Medicine (SEQCML), Analytical Quality Commission, Barcelona, Spain.,Department of Laboratory Medicine, La Paz University Hospital, Madrid, Spain
| | - Pilar Fernández-Calle
- Spanish Society of Laboratory Medicine (SEQCML), Analytical Quality Commission, Barcelona, Spain.,Department of Laboratory Medicine, La Paz University Hospital, Madrid, Spain
| | - Maria Carmen Perich
- Spanish Society of Laboratory Medicine (SEQCML), Analytical Quality Commission, Barcelona, Spain
| | - Margarida Simon
- Spanish Society of Laboratory Medicine (SEQCML), Analytical Quality Commission, Barcelona, Spain.,Consortium of Laboratory Intercomarcal Alt Penedès and Garraf l'Anoia, Vilafranca del Penedès, Spain
| | - Niels Jonker
- Certe-Wilhelmina Ziekenhuis Assen, Assen, The Netherlands
| | - Berna Aslan
- Institute for Quality Management in Healthcare (IQMH), Centre for Proficiency Testing, Toronto, Ontario, Canada
| | | | - Sverre Sandberg
- Department of Medical Biochemistry and Pharmacology, Norwegian Porphyria Centre, Haukeland University Hospital, Bergen, Norway.,Norwegian Organization for Quality Improvement of Laboratory Examinations (NOKLUS), Haraldsplass Deaconess Hospital, Bergen, Norway.,Department of Global Health and Primary Care, Faculty of Medicine, University of Bergen, Bergen, Norway
| | - Aasne K Aarsand
- Department of Medical Biochemistry and Pharmacology, Norwegian Porphyria Centre, Haukeland University Hospital, Bergen, Norway.,Norwegian Organization for Quality Improvement of Laboratory Examinations (NOKLUS), Haraldsplass Deaconess Hospital, Bergen, Norway
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2
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Coşkun A, Aarsand AK, Sandberg S, Guerra E, Locatelli M, Díaz-Garzón J, Fernandez-Calle P, Ceriotti F, Jonker N, Bartlett WA, Carobene A. Within- and between-subject biological variation data for tumor markers based on the European Biological Variation Study. Clin Chem Lab Med 2021; 60:543-552. [PMID: 33964202 DOI: 10.1515/cclm-2021-0283] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 04/27/2021] [Indexed: 12/15/2022]
Abstract
OBJECTIVES Reliable biological variation (BV) data are required for the clinical use of tumor markers in the diagnosis and monitoring of treatment effects in cancer. The European Biological Variation Study (EuBIVAS) was established by the EFLM Biological Variation Working Group to deliver BV data for clinically important measurands. In this study, EuBIVAS-based BV estimates are provided for cancer antigen (CA) 125, CA 15-3, CA 19-9, carcinoembryonic antigen, cytokeratin-19 fragment, alpha-fetoprotein and human epididymis protein 4. METHODS Subjects from five European countries were enrolled in the study, and weekly samples were collected from 91 healthy individuals (53 females and 38 males; 21-69 years old) for 10 consecutive weeks. All samples were analyzed in duplicate within a single run. After excluding outliers and homogeneity analysis, the BVs of tumor markers were determined by CV-ANOVA on trend-corrected data, when relevant (Røraas method). RESULTS Marked individuality was found for all tumor markers. CYFRA 21-1 was the measurand with the highest index of individuality (II) at 0.67, whereas CA 19-9 had the lowest II at 0.07. The CV I s of HE4, CYFRA 21-1, CA 19-9, CA 125 and CA 15-3 of pre- and postmenopausal females were significantly different from each other. CONCLUSIONS This study provides updated BV estimates for several tumor markers, and the findings indicate that marked individuality is characteristic. The use of reference change values should be considered when monitoring treatment of patients by means of tumor markers.
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Affiliation(s)
- Abdurrahman Coşkun
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Department of Medical Biochemistry Atasehir, School of Medicine, Acibadem Mehmet Ali Aydınlar University, Istanbul, Turkey
| | - Aasne K Aarsand
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Department of Medical Biochemistry and Pharmacology, Norwegian Porphyria Centre (NAPOS), Haukeland University Hospital, Bergen, Norway.,Norwegian Organization for Quality Improvement of Laboratory Examinations (NOKLUS), Haraldsplass Deaconess Hospital, Bergen, Norway
| | - Sverre Sandberg
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Department of Medical Biochemistry and Pharmacology, Norwegian Porphyria Centre (NAPOS), Haukeland University Hospital, Bergen, Norway.,Norwegian Organization for Quality Improvement of Laboratory Examinations (NOKLUS), Haraldsplass Deaconess Hospital, Bergen, Norway.,Department of Global Health and Primary Care, Faculty of Medicine, University of Bergen, Bergen, Norway
| | - Elena Guerra
- Servizio di Medicina di Laboratorio, Ospedale San Raffaele, Milan, Italy
| | - Massimo Locatelli
- Servizio di Medicina di Laboratorio, Ospedale San Raffaele, Milan, Italy
| | - Jorge Díaz-Garzón
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Department of Laboratory Medicine, La Paz University Hospital, Milan, Italy.,Analytical Quality Commission, Spanish Society of Laboratory Medicine (SEQCML), Barcelona, Spain
| | - Pilar Fernandez-Calle
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Department of Laboratory Medicine, La Paz University Hospital, Milan, Italy.,Analytical Quality Commission, Spanish Society of Laboratory Medicine (SEQCML), Barcelona, Spain
| | - Ferruccio Ceriotti
- Central Laboratory, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Niels Jonker
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Certe, Wilhelmina Ziekenhuis Assen, Assen, The Netherlands
| | - William A Bartlett
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Blood Sciences, Ninewells Hospital & Medical School, Dundee, UK
| | - Anna Carobene
- EFLM Working Group on Biological Variation, Milan, Italy.,EFLM Task Group for the Biological Variation Database, Milan, Italy.,Servizio Medicina di Laboratorio, Ospedale San Raffaele, Milan, Italy
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3
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Performance of seven criteria to assess CA125 increments among ovarian cancer patients monitored during first-line chemotherapy and the post-therapy follow-up period. Future Sci OA 2017; 3:FSO216. [PMID: 28884012 PMCID: PMC5583662 DOI: 10.4155/fsoa-2017-0023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 04/24/2017] [Indexed: 12/20/2022] Open
Abstract
Aim: To investigate seven CA125 criteria to monitor progressive ovarian cancer among patients with stage IC–IV disease. Materials & methods: Four criteria were used to asses CA125 increments starting from concentrations ≥35 U/ml and three criteria to asses increments starting from concentrations <35 U/ml. Results: A total of 231 patients were allocated to CA125 monitoring. The performances of the CA125 criteria were similar with sensitivities of 30–55%, negative predictive values of 28–46%, positive predictive values of 90–100% and median lead times of 26–87 days. Conclusion: The criteria showed low sensitivity and inability to exclude progressive ovarian cancer. The study suggests that CA125 information cannot stand alone but should be considered used in conjunction with other investigative procedures. Few have validated the CA125 progression criteria proposed by Rustin et al. in 1996 and in 2001. These two criteria were officially recommended by the Gynecological Cancer Intergroup to be incorporated into clinical trials in 2010. Among other criteria, we validated the Gynecological Cancer Intergroup CA125 progression criteria in an ovarian cancer population regarding sensitivity, specificity, positive predictive value and negative predictive value. We found that the criteria had low sensitivity and ability to exclude tumor growth. We believe that the clinical utility of CA125 may be questioned, and there is a need for supplementary markers and alternative assessment criteria.
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Joob B, Wiwanitkit V. Serum Prolactin and CA-125 Levels in Peritoneal Endometriosis. Gynecol Obstet Invest 2015; 80:216. [PMID: 26338345 DOI: 10.1159/000438861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 07/20/2015] [Indexed: 11/19/2022]
Affiliation(s)
- Beuy Joob
- Sanitation 1 Medical Academic Center, Bangkok, Thailand
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5
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Lund F, Petersen PH, Fraser CG, Sölétormos G. Calculation of limits for significant bidirectional changes in two or more serial results of a biomarker based on a computer simulation model. Ann Clin Biochem 2014; 52:434-40. [DOI: 10.1177/0004563214555163] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2014] [Indexed: 11/15/2022]
Abstract
Background Reference change values provide objective tools to assess the significance of a change in two consecutive results of a biomarker from an individual. However, in practice, more results are usually available and using the reference change value concept on more than two results will increase the number of false positive results. Methods A computer simulation model was developed using Excel. Based on 10,000 simulated measurements among healthy individuals, a series of up to 20 results of a biomarker from each individual was generated using different values for the within-subject biological variation plus the analytical variation. Each new result in this series was compared to the initial result. These successive serial differences were computed to give limits for significant bidirectional changes with constant cumulated maximum probabilities of 95% (p < 0.05) and 99% (p < 0.01). Results From an individual factors used to multiply the first result were calculated to create limits for constant cumulated significant changes. The factors were shown to become a function of the number of results included and the total coefficient of variation. Conclusions The first result should be multiplied by the appropriate factors for increase and decrease to give the limits for a significant bidirectional change in several consecutive measurements.
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Affiliation(s)
- Flemming Lund
- Department of Clinical Biochemistry, North Zealand Hospital, University of Copenhagen, Hillerød, Denmark
| | - Per Hyltoft Petersen
- Department of Clinical Biochemistry, North Zealand Hospital, University of Copenhagen, Hillerød, Denmark
- Norwegian Quality Improvement of Primary Care Laboratories (NOKLUS), Section for General Practice, University of Bergen, Bergen, Norway
| | - Callum G Fraser
- Centre for Research into Cancer Prevention and Screening, University of Dundee, Dundee, Scotland
| | - György Sölétormos
- Department of Clinical Biochemistry, North Zealand Hospital, University of Copenhagen, Hillerød, Denmark
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6
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Lund F, Petersen PH, Fraser CG, Sölétormos G. Calculation of limits for significant unidirectional changes in two or more serial results of a biomarker based on a computer simulation model. Ann Clin Biochem 2014; 52:237-44. [DOI: 10.1177/0004563214534636] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Background Reference change values (RCVs) were introduced more than 30 years ago and provide objective tools for assessment of the significance of differences in two consecutive results from an individual. However, in practice, more results are usually available for monitoring, and using the RCV concept on more than two results will increase the number of false-positive results. Therefore, a simple method is needed to interpret the significance of a difference when all available serial biomarker results are considered. Methods A computer simulation model using Excel was developed. Based on 10,000 simulated data from healthy individuals, a series of up to 20 results from an individual was generated using different values for the within-subject biological variation plus the analytical variation. Each new result in this series was compared to the initial measurement result. These successive serial relative differences were computed to give limits for significant unidirectional differences with a constant cumulated maximum probability of both 95% ( P < 0.05) and 99% ( P < 0.01). Results Factors used to multiply the first result from an individual were calculated to create the limits for constant cumulated significant differences. The factors were shown to become a simple function of the number of results and the total coefficient of variation. Conclusions To interpret unidirectional differences in two or more serial results of a biomarker, the limits for significances are easily calculated using the presented factors. The first result is multiplied by the appropriate factor for increase or decrease, which gives the limits for a significant difference.
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Affiliation(s)
- Flemming Lund
- Department of Clinical Biochemistry, North Zealand Hospital, University of Copenhagen, Hillerød, Denmark
| | - Per Hyltoft Petersen
- Department of Clinical Biochemistry, North Zealand Hospital, University of Copenhagen, Hillerød, Denmark
- Norwegian Quality Improvement of Primary Care Laboratories (NOKLUS), Section for General Practice, University of Bergen, Bergen, Norway
| | - Callum G Fraser
- Centre for Research into Cancer Prevention and Screening, University of Dundee, Dundee, Scotland
| | - György Sölétormos
- Department of Clinical Biochemistry, North Zealand Hospital, University of Copenhagen, Hillerød, Denmark
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Development of multiplexed bead-based immunoassays for the detection of early stage ovarian cancer using a combination of serum biomarkers. PLoS One 2012; 7:e44960. [PMID: 22970327 PMCID: PMC3438175 DOI: 10.1371/journal.pone.0044960] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 08/10/2012] [Indexed: 12/13/2022] Open
Abstract
CA125 as a biomarker of ovarian cancer is ineffective for the general population. The aim of this study was to evaluate multiplexed bead-based immunoassay of multiple ovarian cancer-associated biomarkers such as transthyretin and apolipoprotein A1, together with CA125, to improve the identification and evaluation of prognosis of ovarian cancer. We measured the serum levels of CA125, transthyretin, and apolipoprotein A1 from the serum of 61 healthy individuals, 84 patients with benign ovarian disease, and 118 patients with ovarian cancer using a multiplex liquid assay system, Luminex 100. The results were then analyzed according to healthy and/or benign versus ovarian cancer subjects. When CA125 was combined with the other biomarkers, the overall sensitivity and specificity were significantly improved in the ROC curve, which showed 95% and 97% sensitivity and specificity, respectively. At 95% specificity for all stages the sensitivity increased to 95.5% compared to 67% for CA125 alone. For stage I+II, the sensitivity increased from 30% for CA125 alone to 93.9%. For stage III+IV, the corresponding values were 96.5% and 91.6%, respectively. Also, the three biomarkers were sufficient for maximum separation between noncancer (healthy plus benign group) and stage I+II or all stages (I-IV) of disease. The new combination of transthyretin, and apolipoprotein A1 with CA125 improved both the sensitivity and the specificity of ovarian cancer diagnosis compared with those of individual biomarkers. These findings suggest the benefit of the combination of these markers for the diagnosis of ovarian cancer.
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Advantages of the lognormal approach to determining reference change values for N-terminal propeptide B-type natriuretic peptide. Clin Chim Acta 2012; 413:544-7. [DOI: 10.1016/j.cca.2011.11.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 11/10/2011] [Accepted: 11/12/2011] [Indexed: 11/17/2022]
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9
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Díaz-Padilla I, Razak ARA, Minig L, Bernardini MQ, del Campo JM. Prognostic and predictive value of CA-125 in the primary treatment of epithelial ovarian cancer: potentials and pitfalls. Clin Transl Oncol 2012; 14:15-20. [DOI: 10.1007/s12094-012-0756-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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11
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Domingo-Domènech J, Molina R, Castel T, Montagut C, Puig S, Conill C, Martí R, Vera M, Auge JM, Malvehy J, Grau JJ, Gascon P, Mellado B. Serum Protein S-100 Predicts Clinical Outcome in Patients with Melanoma Treated with Adjuvant Interferon – Comparison with Tyrosinase RT-PCR. Oncology 2005; 68:341-9. [PMID: 16020961 DOI: 10.1159/000086973] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2004] [Accepted: 10/03/2004] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To study the clinical value of the determination of serum S-100 protein as a single tumor marker or in combination with tyrosinase RT-PCR in patients with melanoma receiving adjuvant interferon. PATIENTS AND METHODS Patients were tested for serum S-100 protein luminoimmunometric assay and for blood tyrosinase mRNA (RT-PCR), before starting interferon and every 2-3 months thereafter. RESULTS One hundred and six patients (stage IIA, 27; IIB, 19; III, 49; and IV, 11) were included in the study. Median follow-up was 51 months (range 2-76). In the univariate analysis, under treatment S-100 > or =0.15 microg/l and a positive RT-PCR correlated with a lower disease-free survival and overall survival (OS). In the multivariate analysis, clinical stage, under therapy positive RT-PCR and S-100 levels > or =0.15 mug/ml, were independent prognostic factors for OS. The hazard ratio for OS was 3.9 (95% CI, 1.67-9.15; p = 0.004) and 2.2 (95% CI, 1.05-4.6; p = 0.016) for S-100 > or =0.15 microg/l and positive RT-PCR, respectively. When both techniques where combined, a positive RT-PCR indicated a poorer clinical outcome only in patients with S-100 <0.15 microg/l. CONCLUSIONS S-100 > or =0.15 microg/l and a positive RT-PCR during adjuvant interferon therapy indicate a high risk of death in resected melanoma patients. S-100 determination has a higher positive predictive value than RT-PCR, while tyrosinase RT-PCR adds prognostic information in patients with S-100 <0.15 microg/l.
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Affiliation(s)
- J Domingo-Domènech
- Medical Oncology Department, Biochemistry Department, Hospital Clínic, IDIBAPS, Melanoma Group, Barcelona, Spain.
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Trapé J, Pérez de Olaguer J, Buxó J, López L. Biological Variation of Tumor Markers and Its Application in the Detection of Disease Progression in Patients with Non-Small Cell Lung Cancer. Clin Chem 2005; 51:219-22. [PMID: 15613716 DOI: 10.1373/clinchem.2004.040659] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jaume Trapé
- Clinical Laboratory, Hospital Sant Joan de Déu, Althaia Xarxa Assistencial de Manresa, 08243 Barcelona, Spain.
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13
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Iglesias Canadell N, Hyltoft Petersen P, Jensen E, Ricós C, Jørgensen PE. Reference change values and power functions. ACTA ACUST UNITED AC 2004; 42:415-22. [PMID: 15147152 DOI: 10.1515/cclm.2004.073] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractRepeated samplings and measurements in the monitoring ofpatients to look for changes are common clinical problems. The “reference change value”, calculated as z
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14
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Abstract
A soluble plasma form of CD163 (sCD163) was recently identified. The protein has anti-inflammatory effects in vitro and is elevated in patients with myelo-monocytic leukaemia and infection. For rational use and evaluation of this potential new quantity it is important to have knowledge of its biological variability and to use a methodology that has a sufficiently analytical quality. The day-to-day and diurnal biological variabilities of sCD163 were studied in 12 healthy people using a sandwich ELISA. The within-run-, between run- and total analytical coefficients of variation were estimated to 3.6%, 4.8% and 6.0%, respectively. The day-to-day within-subject biological variation was estimated to 9.0%, and the between-subject biological variation to 35.9%. A diurnal variation in sCD163 concentrations with 14% lower values in the night (supine position) was observed. The ratio between total analytical variation and within-subject biological variation was 0.67. The index of individuality, calculated as the ratio between within-subject biological variation and between-subject biological variation, was low and similar to complement factors and immunoglobulins. A low index of individuality is important in a monitoring situation where small changes from the set point of the individual can be detected in serial measurements. For this purpose, the critical difference for a series of results in the same patient (significant at p < 0.05) was calculated to 30% for samples taken on different days and measured in separate runs.
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Affiliation(s)
- H J Møller
- Department of Clinical Biochemistry, AAS Aarhus University Hospital, Denmark.
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