CLB-08991; No. of pages: 2; 4C: Clinical Biochemistry xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem
21 days 10 days
0.04 0.04 57 0.19 0.19 95 1.7 1.7 100 4.1 4.0–4.1 100 0.07 0.06–0.07 100 0.19 0.19 95 1.8 1.8 106 3.8 3.7–3.8 93
1 day 0h
0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100 0.06 0.06 86 0.19 0.19 95 1.8 1.8 106 4.6 4.5–4.6 112 0.06 0.06 86 0.20 0.19–0.20 100 1.9 1.9 112 4.5 4.5 110 0.07 0.07 100 0.20 0.20 100 1.9 1.9 112 4.2 4.2 102 0.07 0.07 100 0.20 0.19–0.21 100 1.8 1.8 106 4.4 4.3–4.4 107 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.0–4.1 100 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100 0.06 0.06 86 0.20 0.19–0.20 100 1.8 1.8 106 4.6 4.5–4.6 112 0.07 0.06–0.07 100 0.20 0.20 100 1.8 1.8 106 4.2 4.2 102 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.0–4.1 100
3 days 1 day 10 h
High (mM)
Low (mM) Lactate
High (mM)
Mean Range % of baseline Mean Range % of baseline Mean Range % of baseline Mean Range % of baseline Low (mM) Pyruvate
6h
10 h
1 day
3 days
6h
4 °C (n = 2)
0h
Room temperature (n = 2)
0h
Sample Analyte
Table 1 Stability of pyruvate and lactate in pooled clear CSF specimens at various storage conditions.
Pyruvate and lactate are two key intermediary metabolites of carbohydrate metabolism. Measurement of pyruvate and/or lactate in cerebrospinal fluid (CSF) may provide valuable information for diagnosing pathologies in the central nervous system (CNS) [1]. However, the stability data of lactate and pyruvate in CSF is scarce in literature, especially for pyruvate which could not be found at the time of this manuscript preparation. Lactate in CSF was found to be stable at 4 °C for 24 h [2], while blood contamination in CSF causes significant increase of lactate concentration when incubated at 37 °C for 6 and 24 h [3]. Therefore, storage requirements by clinical laboratories are diverse. For lactate, most require immediate refrigeration and staying frozen for long term storage. For CSF pyruvate, some accept specimens kept at room temperature for 7 days while others only accept specimens stored refrigerated for short term and frozen for extended storage. In the current study, we investigated in vitro stability of pyruvate and lactate at various clinical laboratory storage conditions. Measurements of pyruvate and lactate in CSF were by enzymatic assays. We arbitrarily used 15% as the significant change cutoff. Due to large specimen quantity needed for the pyruvate assay and the limited CSF volumes that were available from individual collections, we pooled leftover patient specimens for this investigation. The use of leftover specimens in this study was approved by the Institutional Review Board. First, a pool of 50 mL CSF was evenly divided into two batches, which were labeled “low” and “high”. The “low” was unaltered while “high” was spiked with pyruvate and lactate. Both were aliquoted, capped, and stored at room temperature, 4 °C, or − 20 °C. Aliquots in duplicates were then deproteinized and analyzed at the specified time points. As shown in Table 1, pyruvate was stable for 3 days at room temperature, 21 days at 4 °C, and only 24 h at −20 °C. Lactate was stable for the entire study periods (3 days at room temperature, 21 days at 4 °C, and 21 days at − 20 °C). This confirms and extends the findings by Dujmovic and Deisenhammer who showed that lactate in CSF is stable at 4 °C for 24 h [2]. Contrary to the requirements posted by some clinical laboratories, pyruvate was found unstable after stored at − 20 °C for 10 days. Second, we repeated the same experiments in a CSF pool tinted with blood during sample collection. We found that the stability patterns of pyruvate and lactate did not differ significantly, which agreed with the findings by Dujmovic and Deisenhammer [2].
10 days
To the Editor:
0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100
21 days
−20 °C (n = 2)
Keywords: Lactate Pyruvate Cerebrospinal fluid Stability
0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100
Stability of lactate and pyruvate in cerebrospinal fluid under typical clinical laboratory storage conditions
0.04 0.04 57 0.17 0.17 85 1.6 1.6 94 3.8 3.8 93
Letter to the Editor
http://dx.doi.org/10.1016/j.clinbiochem.2015.03.018 0009-9120/© 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
Please cite this article as: Zhang L, et al, Stability of lactate and pyruvate in cerebrospinal fluid under typical clinical laboratory storage conditions, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.03.018
2
Letter to the Editor
In conclusion, pyruvate in CSF was found stable for 3 days at room temperature, 21 days at 4 °C, and only 24 h at − 20 °C while lactate was stable for the entire study periods (3 days at room temperature, 21 days at 4 °C, and 21 days at − 20 °C). CSF specimens for pyruvate analysis should not be stored at −20 °C for long term storage.
References [1] Benoist JF, Alberti C, Leclercq S, Rigal O, Jean-Louis R, Ogier de Baulny H, et al. Cerebrospinal fluid lactate and pyruvate concentrations and their ratio in children: agerelated reference intervals. Clin Chem 2003;49(3):487–94. [2] Dujmovic I, Deisenhammer F. Stability of cerebrospinal fluid/serum glucose ratio and cerebrospinal fluid lactate concentrations over 24 h: analysis of repeated measurements. Clin Chem Lab Med 2010;48(2):209–12. [3] Venkatesh B, Morgan TJ, Boots RJ, Hall J, Siebert D. Interpreting CSF lactic acidosis: effect of erythrocytes and air exposure. Crit Care Resusc 2003;5(3):177–81.
Lin Zhang Cleveland State University, Cleveland, OH, USA Jessica Gabler ThermoFisher Scientific, San Jose, CA, USA Drew Payto Cleveland Clinic, Cleveland, OH, USA Sihe Wang Cleveland State University, Cleveland, OH, USA Cleveland Clinic, Cleveland, OH, USA Corresponding author at: Department of Clinical Pathology/L11, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA. Fax: +1 216 444 4414. E-mail address: [email protected]. 10 March 2015 Available online xxxx
Please cite this article as: Zhang L, et al, Stability of lactate and pyruvate in cerebrospinal fluid under typical clinical laboratory storage conditions, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.03.018
Contents lists available at ScienceDirect
Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem
21 days 10 days
0.04 0.04 57 0.19 0.19 95 1.7 1.7 100 4.1 4.0–4.1 100 0.07 0.06–0.07 100 0.19 0.19 95 1.8 1.8 106 3.8 3.7–3.8 93
1 day 0h
0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100 0.06 0.06 86 0.19 0.19 95 1.8 1.8 106 4.6 4.5–4.6 112 0.06 0.06 86 0.20 0.19–0.20 100 1.9 1.9 112 4.5 4.5 110 0.07 0.07 100 0.20 0.20 100 1.9 1.9 112 4.2 4.2 102 0.07 0.07 100 0.20 0.19–0.21 100 1.8 1.8 106 4.4 4.3–4.4 107 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.0–4.1 100 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100 0.06 0.06 86 0.20 0.19–0.20 100 1.8 1.8 106 4.6 4.5–4.6 112 0.07 0.06–0.07 100 0.20 0.20 100 1.8 1.8 106 4.2 4.2 102 0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.0–4.1 100
3 days 1 day 10 h
High (mM)
Low (mM) Lactate
High (mM)
Mean Range % of baseline Mean Range % of baseline Mean Range % of baseline Mean Range % of baseline Low (mM) Pyruvate
6h
10 h
1 day
3 days
6h
4 °C (n = 2)
0h
Room temperature (n = 2)
0h
Sample Analyte
Table 1 Stability of pyruvate and lactate in pooled clear CSF specimens at various storage conditions.
Pyruvate and lactate are two key intermediary metabolites of carbohydrate metabolism. Measurement of pyruvate and/or lactate in cerebrospinal fluid (CSF) may provide valuable information for diagnosing pathologies in the central nervous system (CNS) [1]. However, the stability data of lactate and pyruvate in CSF is scarce in literature, especially for pyruvate which could not be found at the time of this manuscript preparation. Lactate in CSF was found to be stable at 4 °C for 24 h [2], while blood contamination in CSF causes significant increase of lactate concentration when incubated at 37 °C for 6 and 24 h [3]. Therefore, storage requirements by clinical laboratories are diverse. For lactate, most require immediate refrigeration and staying frozen for long term storage. For CSF pyruvate, some accept specimens kept at room temperature for 7 days while others only accept specimens stored refrigerated for short term and frozen for extended storage. In the current study, we investigated in vitro stability of pyruvate and lactate at various clinical laboratory storage conditions. Measurements of pyruvate and lactate in CSF were by enzymatic assays. We arbitrarily used 15% as the significant change cutoff. Due to large specimen quantity needed for the pyruvate assay and the limited CSF volumes that were available from individual collections, we pooled leftover patient specimens for this investigation. The use of leftover specimens in this study was approved by the Institutional Review Board. First, a pool of 50 mL CSF was evenly divided into two batches, which were labeled “low” and “high”. The “low” was unaltered while “high” was spiked with pyruvate and lactate. Both were aliquoted, capped, and stored at room temperature, 4 °C, or − 20 °C. Aliquots in duplicates were then deproteinized and analyzed at the specified time points. As shown in Table 1, pyruvate was stable for 3 days at room temperature, 21 days at 4 °C, and only 24 h at −20 °C. Lactate was stable for the entire study periods (3 days at room temperature, 21 days at 4 °C, and 21 days at − 20 °C). This confirms and extends the findings by Dujmovic and Deisenhammer who showed that lactate in CSF is stable at 4 °C for 24 h [2]. Contrary to the requirements posted by some clinical laboratories, pyruvate was found unstable after stored at − 20 °C for 10 days. Second, we repeated the same experiments in a CSF pool tinted with blood during sample collection. We found that the stability patterns of pyruvate and lactate did not differ significantly, which agreed with the findings by Dujmovic and Deisenhammer [2].
10 days
To the Editor:
0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100
21 days
−20 °C (n = 2)
Keywords: Lactate Pyruvate Cerebrospinal fluid Stability
0.07 0.07 100 0.20 0.20 100 1.7 1.7 100 4.1 4.1 100
Stability of lactate and pyruvate in cerebrospinal fluid under typical clinical laboratory storage conditions
0.04 0.04 57 0.17 0.17 85 1.6 1.6 94 3.8 3.8 93
Letter to the Editor
http://dx.doi.org/10.1016/j.clinbiochem.2015.03.018 0009-9120/© 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
Please cite this article as: Zhang L, et al, Stability of lactate and pyruvate in cerebrospinal fluid under typical clinical laboratory storage conditions, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.03.018
2
Letter to the Editor
In conclusion, pyruvate in CSF was found stable for 3 days at room temperature, 21 days at 4 °C, and only 24 h at − 20 °C while lactate was stable for the entire study periods (3 days at room temperature, 21 days at 4 °C, and 21 days at − 20 °C). CSF specimens for pyruvate analysis should not be stored at −20 °C for long term storage.
References [1] Benoist JF, Alberti C, Leclercq S, Rigal O, Jean-Louis R, Ogier de Baulny H, et al. Cerebrospinal fluid lactate and pyruvate concentrations and their ratio in children: agerelated reference intervals. Clin Chem 2003;49(3):487–94. [2] Dujmovic I, Deisenhammer F. Stability of cerebrospinal fluid/serum glucose ratio and cerebrospinal fluid lactate concentrations over 24 h: analysis of repeated measurements. Clin Chem Lab Med 2010;48(2):209–12. [3] Venkatesh B, Morgan TJ, Boots RJ, Hall J, Siebert D. Interpreting CSF lactic acidosis: effect of erythrocytes and air exposure. Crit Care Resusc 2003;5(3):177–81.
Lin Zhang Cleveland State University, Cleveland, OH, USA Jessica Gabler ThermoFisher Scientific, San Jose, CA, USA Drew Payto Cleveland Clinic, Cleveland, OH, USA Sihe Wang Cleveland State University, Cleveland, OH, USA Cleveland Clinic, Cleveland, OH, USA Corresponding author at: Department of Clinical Pathology/L11, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA. Fax: +1 216 444 4414. E-mail address: [email protected]. 10 March 2015 Available online xxxx
Please cite this article as: Zhang L, et al, Stability of lactate and pyruvate in cerebrospinal fluid under typical clinical laboratory storage conditions, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.03.018
