Clin Chem Lab Med 2015; 53(7): e169–e171
Letter to the Editor Joffrey Feriel, Fréderic Adamo, Denis Monneret, Virginie Trehel-Tursis, Séverine Favard, Chantal Tsé, Louis Puybasset, Dominique Bonnefont-Rousselot and Françoise Imbert-Bismut*
S100B protein concentration measurement according to two different immunoassays DOI 10.1515/cclm-2014-1090 Received November 6, 2014; accepted January 5, 2015; previously published online February 13, 2015
Keywords: brain damage; cut-off; immunoassays; kinetics; S-100 β protein (S100B). To the Editor, Acute brain damages are a major public health problem, as evidenced by 200,000 traumatic brain injuries per year in France [1]. Diagnosis of brain damage is mainly based on clinical examination and computed tomography (CT) scan, which still have some limitations. For example, the patient’s neurological status can be difficult to assess due to the presence of toxics or hypnotics. CT scan remains the gold standard to appreciate local damage but is onerous and sometimes unavailable in emergency. These limitations have led clinicians and researchers to look for biomarkers of interest for the diagnosis of brain damage. The S100 β protein (S100B) has emerged as a relevant biomarker of acute neurological disorders. It has been increasingly studied these last few years, especially as automated assays are available to obtain results quickly [2–4]. *Corresponding author: Françoise Imbert-Bismut, AP-HP, Hôpital Pitié-Salpêtrière, Service de Biochimie Métabolique, Paris, 75013, France, E-mail: [email protected] Joffrey Feriel, Fréderic Adamo, Denis Monneret, Séverine Favard and Chantal Tsé: AP-HP, Hôpital Pitié-Salpêtrière, Service de Biochimie Métabolique, Paris, France Virginie Trehel-Tursis and Louis Puybasset: AP-HP, Hôpital PitiéSalpêtrière, Département d’Anesthèsie-Réanimation, Paris, France Dominique Bonnefont-Rousselot: AP-HP, Hôpital Pitié-Salpêtrière, Service de Biochimie Métabolique, Paris, France; UPMC Université Paris 6 UMRS_1166 ICAN, Paris, France; and Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Paris, France
S100B is a calcium binding protein belonging to the protein S100 group discovered by Moore in 1965 [5]. The S100B subtype predominates in nervous tissue, including astrocytes and Schwann cells. Its circulating level has been shown to be directly proportional to the severity of brain injury, although not totally neuro-specific (also present, to a lesser extent, in long bones, muscles [6]). After a head injury, S100B crosses the impaired bloodbrain barrier and increases in blood with a concentration 10 times lower than in cerebral spinal fluid [7]. Nevertheless, S100B blood concentration depends on the method used for the measurement, as shown in a few analytical studies [8, 9]. The aim of the study was to compare the results and kinetics of serum S100B concentrations in patients with brain damage, daily assayed on Modular E170® (Roche Diagnostics, Mannheim, Germany) and Liaison® (Diasorin, Antony, France). Nineteen patients hospitalized in the neurosurgical intensive care unit of the Pitié-Salpêtrière Hospital between May and September 2011 were included in this study, with a daily assessment of S100B for 7 consecutive days. Among them, eight patients were admitted for traumatic brain injury, six for subarachnoid hemorrhage, two for intra-parenchymal hemorrhage, two for coma and one for intracranial hypertension. A first S100B measurement was performed on fresh serum on Modular E170®, and the remaining serum volume was stored at –20 °C, for further S100B measurements on Liaison® analyzer. The serum S100B concentration was determined using sandwich immunoassays; an electrochemiluminometric sandwich immunoassay on Modular E170® and a chemiluminometric one on Liaison®. The reaction involves two antibodies (Abs): a biotinylated Ab and a rutheniumlabeled (on Modular E170®) or isoluminol-labeled (on Liaison®) Ab. The biotinylated Ab allows the attachment to a solid support (through a streptavidin – biotin connection). The ruthenium or isoluminol-labeled Ab allows the generation of a measurable signal. The calibration range is 0.005–39 μg/L for Modular E170®, with an intra-assay
A
3.0
Liaison S100B, µg/L
e170 Feriel et al.: S100B measurement according to two different immunoassays
2.5
Group 1 1.0 0.8 S100B, µg/L
2.0 1.5 1.0 0.5
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6
0.0
0.5
1.0 1.5 2.0 Modular S100B, µg/L
2.5
3.0
0.0 1
2
3
4 Days
5
6
7
5
6
7
5
6
Group 2 2.0 +1.96 SD 0.75
1.5
Mean 0.21 -1.96 SD -0.32 0.0
0.5 1.0 1.5 2.0 Average of liaison and modular S100B, µg/L
1.0
0.5
2.5 0.0
200 +1.96 SD 149.4
150
1
2
3
4 Days Group 3
0.6
100 Mean 63.7
50
0.4 0
S100B, µg/L
Liaison – modular S100B, µg/L/average, %
Liaison – modular S100B, µg/L
B
0.4 0.2
S100B, µg/L
0.0
0.6
-1.96 SD -22.0
-50 -100 0.0
0.5 1.0 1.5 2.0 Average of liaison and modular S100B, µg/L
0.2
2.5
Figure 1: Comparison of serum S100B concentrations quantified by Liaison® and Modular E170® using (A) Passing-Bablok linear regression and (B) Bland-Altman plot.
precision
Letter to the Editor Joffrey Feriel, Fréderic Adamo, Denis Monneret, Virginie Trehel-Tursis, Séverine Favard, Chantal Tsé, Louis Puybasset, Dominique Bonnefont-Rousselot and Françoise Imbert-Bismut*
S100B protein concentration measurement according to two different immunoassays DOI 10.1515/cclm-2014-1090 Received November 6, 2014; accepted January 5, 2015; previously published online February 13, 2015
Keywords: brain damage; cut-off; immunoassays; kinetics; S-100 β protein (S100B). To the Editor, Acute brain damages are a major public health problem, as evidenced by 200,000 traumatic brain injuries per year in France [1]. Diagnosis of brain damage is mainly based on clinical examination and computed tomography (CT) scan, which still have some limitations. For example, the patient’s neurological status can be difficult to assess due to the presence of toxics or hypnotics. CT scan remains the gold standard to appreciate local damage but is onerous and sometimes unavailable in emergency. These limitations have led clinicians and researchers to look for biomarkers of interest for the diagnosis of brain damage. The S100 β protein (S100B) has emerged as a relevant biomarker of acute neurological disorders. It has been increasingly studied these last few years, especially as automated assays are available to obtain results quickly [2–4]. *Corresponding author: Françoise Imbert-Bismut, AP-HP, Hôpital Pitié-Salpêtrière, Service de Biochimie Métabolique, Paris, 75013, France, E-mail: [email protected] Joffrey Feriel, Fréderic Adamo, Denis Monneret, Séverine Favard and Chantal Tsé: AP-HP, Hôpital Pitié-Salpêtrière, Service de Biochimie Métabolique, Paris, France Virginie Trehel-Tursis and Louis Puybasset: AP-HP, Hôpital PitiéSalpêtrière, Département d’Anesthèsie-Réanimation, Paris, France Dominique Bonnefont-Rousselot: AP-HP, Hôpital Pitié-Salpêtrière, Service de Biochimie Métabolique, Paris, France; UPMC Université Paris 6 UMRS_1166 ICAN, Paris, France; and Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Paris, France
S100B is a calcium binding protein belonging to the protein S100 group discovered by Moore in 1965 [5]. The S100B subtype predominates in nervous tissue, including astrocytes and Schwann cells. Its circulating level has been shown to be directly proportional to the severity of brain injury, although not totally neuro-specific (also present, to a lesser extent, in long bones, muscles [6]). After a head injury, S100B crosses the impaired bloodbrain barrier and increases in blood with a concentration 10 times lower than in cerebral spinal fluid [7]. Nevertheless, S100B blood concentration depends on the method used for the measurement, as shown in a few analytical studies [8, 9]. The aim of the study was to compare the results and kinetics of serum S100B concentrations in patients with brain damage, daily assayed on Modular E170® (Roche Diagnostics, Mannheim, Germany) and Liaison® (Diasorin, Antony, France). Nineteen patients hospitalized in the neurosurgical intensive care unit of the Pitié-Salpêtrière Hospital between May and September 2011 were included in this study, with a daily assessment of S100B for 7 consecutive days. Among them, eight patients were admitted for traumatic brain injury, six for subarachnoid hemorrhage, two for intra-parenchymal hemorrhage, two for coma and one for intracranial hypertension. A first S100B measurement was performed on fresh serum on Modular E170®, and the remaining serum volume was stored at –20 °C, for further S100B measurements on Liaison® analyzer. The serum S100B concentration was determined using sandwich immunoassays; an electrochemiluminometric sandwich immunoassay on Modular E170® and a chemiluminometric one on Liaison®. The reaction involves two antibodies (Abs): a biotinylated Ab and a rutheniumlabeled (on Modular E170®) or isoluminol-labeled (on Liaison®) Ab. The biotinylated Ab allows the attachment to a solid support (through a streptavidin – biotin connection). The ruthenium or isoluminol-labeled Ab allows the generation of a measurable signal. The calibration range is 0.005–39 μg/L for Modular E170®, with an intra-assay
A
3.0
Liaison S100B, µg/L
e170 Feriel et al.: S100B measurement according to two different immunoassays
2.5
Group 1 1.0 0.8 S100B, µg/L
2.0 1.5 1.0 0.5
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6
0.0
0.5
1.0 1.5 2.0 Modular S100B, µg/L
2.5
3.0
0.0 1
2
3
4 Days
5
6
7
5
6
7
5
6
Group 2 2.0 +1.96 SD 0.75
1.5
Mean 0.21 -1.96 SD -0.32 0.0
0.5 1.0 1.5 2.0 Average of liaison and modular S100B, µg/L
1.0
0.5
2.5 0.0
200 +1.96 SD 149.4
150
1
2
3
4 Days Group 3
0.6
100 Mean 63.7
50
0.4 0
S100B, µg/L
Liaison – modular S100B, µg/L/average, %
Liaison – modular S100B, µg/L
B
0.4 0.2
S100B, µg/L
0.0
0.6
-1.96 SD -22.0
-50 -100 0.0
0.5 1.0 1.5 2.0 Average of liaison and modular S100B, µg/L
0.2
2.5
Figure 1: Comparison of serum S100B concentrations quantified by Liaison® and Modular E170® using (A) Passing-Bablok linear regression and (B) Bland-Altman plot.
precision
