Electrolytes Levels (Na, K, Cl) in Serum Stored at 4°C Temperature
Amalia Nurul Fauziah1, M. Atik Martsiningsih2, Budi Setiawan3,4
1

Pratama Hospital Yogyakarta,
Yogyakarta City, Yogyakarta,
Indonesia
2

D-III of Medical Laboratory
Technology, Poltekkes Kemenkes
Yogyakarta, Yogyakarta, Indonesia
Bachelor’s Degrees in Medical
Laboratory Technology, Poltekkes
Kemenkes Yogyakarta,
Yogyakarta, Indonesia
3

4

Pusat Unggulan IPTEK Inovasi
Teknologi Bidang Kesehatan
Masyarakat (PUI-Novakesmas),
Poltekkes Kemenkes Yogyakarta,
Yogyakarta, Indonesia
Correspondence:
Amalia Nurul Fauziah, Jl
Srandakan Km 01, Pandak, Bantul,
Yogyakarta, Indonesia
Zip Code: 55761
Email: amalianurul112@gmail.com
Received: January 2, 2021
Revised: March 5, 2021
Accepted: June 6, 2021
Published: October 30, 2021
DOI: 10.33086/ijmlst.v3i2.1870

Abstract
The samples used for serum electrolyte measurement should
be analyzed immediately after being received in the
laboratory within 1-2 hours to avoid an increase in the error
of the results. Serum should be stored at 4°C for a period to
prevent damage. The analyst should consider maximum
delay time in the examination to maintain the serum's
quality. This study compared the 2-hour and 3-hour delays
in sodium (Na), potassium (K), and chlorine (Cl) tests. The
method used in this study is an observational analysis with
a cross-sectional study design. The samples in this study
used 35 patient serum residues. The study was conducted in
November 2020 with a continuous sampling technique.
Electrolyte levels in the sample were measured by AVL
9180 Electrolyte Analyzer using Ion-Selective Electrode
(ISE) method. The differences in electrolyte (Na, K, Cl)
levels were analyzed by the Kruskal-Wallis Statistical test at
a 95% confidence level. The results showed that the content
of sodium, potassium, and chlorine were 0.719; 0.976; and
0.772. This study showed that there was no significant
difference in the electrolyte content of sodium (Na),
potassium (K), and chlorine (Cl) in the serum directly
detected from the serum stored at 4°C for 2 hours and 3
hours. In conclusion, it is acceptable to postpone the serum
test for 3 hours with various considerations.
Keywords
Chloride, Delay Time, Potassium, Serum, Sodium.

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited. ©2021 by author.

90

Amalia Nurul Fauziah, et al.

treatment when their body electrolytes are

INTRODUCTION
Fluid and electrolyte balance disorders

imbalanced (9). If not managed properly,

are common in clinical practice, especially in

changes in fluid and electrolyte concentration

hospitals

can cause serious problems.

(1).

The

fluid

amount

and

electrolyte concentration changes can cause a

Laboratory error leads to unnecessary

variety of problems if not appropriately

delays and additional costs by obligatory

managed. The electrolyte tests are usually

repeated samples and causes unnecessary

performed as regular check-ups for specific

suffering

medical conditions, such as decreased renal

analytical errors account for up to 70% of all

function, heart failure, and diarrhea (2–4).

errors in laboratory diagnosis, most of which

Sodium (Na+), Potassium (K+), and

to

patients.

Currently,

pre-

arise from problems in patient preparation,

Chloride (Cl-) are the primary electrolytes

sample

(ions) in the body. Changes in electrolyte

preparation for analysis and storage (10,11).

concentration and or ratio of anions and

The samples used to measure serum

cations will cause changes in cell activity that

electrolytes should be analyzed as soon as

can endanger life (5). Na+ is the primary

possible, preferably within 1-2 hours after

electrolyte of extracellular fluid, which in the

being received in the laboratory. The sodium,

case of hyponatremia or hypernatrium, the

potassium, and chlorine stability will change

Na+ concentration is regulated by the

after a few hours of centrifugation (12).

kidneys. K+ is the central intracellular cation

Proper specimen storage is an option to avoid

and plays a vital role in cell metabolism.

repeated sampling in patients. If the serum

Changes

levels

should be stored for a moment, it should be

(hyperkalemia or hypokalemia) can affect

closed and stored in the refrigerator before

neuromuscular and heart function (6).

analyzing the serum at room temperature

Clinical features of potassium disorder can be

(13).

in

plasma

potassium

collection,

transportation,

and

the most life-threatening disorder compared

The limitation of sample analysis in some

to others (7). Besides, chloride is the primary

laboratories is the delay in sample analysis

extracellular anion in humans. It is essential

after

to maintain serum neutrality, acid-base

condition is due to follow-up requests from

balance, homeostasis of body fluids, osmotic

clinicians, large sample loads, tool damage,

pressure, production of hydrochloric acid

and unavailability of backup equipment in the

(HCl) in the gastrointestinal tract, kidney

laboratory.

function, and electrical activity in muscular

research, the average time required to refer a

activity (8). Someone should give immediate

serum sample to the laboratory is 2 to 3 hours.

centrifugation

According

process.

to

This

preliminary

91

Ina. J. Med. Lab. Sci. Tech. 2021; 3(2): 90–98

the

Amalia Nurul Fauziah, et al.

The study by Baruah et al. (12) also showed

serum was allowed to stand for 30 minutes at

that the validity of the sodium and chlorine

room temperature before the test (13).

results

was

affected

3

hours

after

The samples obtained were centrifuged

centrifugation. In contrast, the validity of the

at 3,000 rpm for 10 minutes. The serum was

potassium results was affected 1 hour after

separated into Eppendorf tubes. Thirty-five

centrifugation. Therefore, it is essential to

serum samples were analyzed for Na+, K+,

find out the differences in the electrolyte

and Cl- levels were measured by AVL

levels of sodium (Na), potassium (K), and

9180 Electrolyte Analyzer using the Ion-

chloride (Cl) in the serum after being stored

Selective Electrode (ISE) method.

for 2 hours and 3 hours at 4oC.

The differences in sodium, potassium
and chloride levels in samples between

MATERIALS AND METHODS
analytical

hours at 4oC) samples were analyzed by a

observational study with a cross-sectional

statistical test. The data obtained were

study design. The study was conducted in

primary data and scaled ratio data. The

November 2020. A total of 35 serum samples

statistical analysis was performed by SPSS

residue

performed

24.0 for Windows. The data was analyzed

chemical examinations in the laboratory of

with a One-Sample Kolmogorov-Smirnov

one hospital in Yogyakarta City, Indonesia

Test. Abnormal result resulting caused by

was collected by consecutive sampling.

data dissemination. Therefore, we were

This

study

from

used

patients

an

who

Inclusion criteria in this study were the

92

direct-used and cold-stored (2 hours and 3

analyzed further by statistical tests, namely

remaining serum from patients examined in

non-parametric

statistical

tests

used K-

the laboratory with a volume of ≥1 mL. The

Independent Samples (Kruskal-Wallis H).

samples used were visually clear, not

The data is presented as tables and statistical

hemolysis, icteric, and lipemic. The research

tests of non-parametric Kruskal-Wallis with

procedure was carried out by inserting a

a confidence level of 95% using statistical

blood sample into the vacutainer tube of the

programs.

clot separator gel. The blood was allowed to

The Ethics Commission has approved

clot at room temperature. Then the sample

this research for Health Research of

serum is grouped into two treatments. We

Politeknik Kesehatan Kementrian Kesehatan

directly examined the first sample group, and

(Poltekkes Kemenkes Yogyakarta) under the

the second sample group was stored in a

Ethics

refrigerator. The serum was stored in a fridge

KEPK/POLKESYO

at 4°C ± 2°C for 2 hours and 3 hours. The

October 20, 2020.

Feasibility

Letter

No.

/0629/X/2020

edated

Ina. J. Med. Lab. Sci. Tech. 2021; 3(2): 90–98

Amalia Nurul Fauziah, et al.

serum

RESULTS

electrolyte

testing

for

several

The average time required to send a

treatments (direct-tested and stored for 2

serum sample to the laboratory was 2-3 hours

hours and 3 hours at 4°C) are shown in Table

(after time for collection). The results of

1.

Table 1. Serum electrolyte level for several treatments (direct-tested and stored for 2 hours and 3
hours at 4° C)
Electrolyte Test

n

Na
Directly tested
35
2h
35
3h
35
K
Directly tested
35
2h
35
3h
35
Cl
Directly tested
35
2h
35
3h
35
Source: Primary Data, 2020

Mean
(mmol/L)

Min
(mmol/L)

Max
(mmol/L)

SD

P-Value

138.7
139.2
139.0

133
134
134

144
146
145

2.64
2.70
2.82

0.719

4.31
4.32
4.31

3.2
3.3
3.3

6.1
6.0
6.0

0.65
0.63
0.63

0.976

103
104
104

96
97
97

110
110
110

3.38
3.24
3.21

0.772

Table 1 present the sodium levels of 2

DISCUSSION

hours-stored-serum (139.2 mmol/L) is 0.5

Fluid and electrolyte balance is crucial

mmol/L higher than directly-tested-serum

for

(138.7 mmol/L). While 3 hour-stored-serum

homeostasis and the successful treatment of

sodium (139.0 mmol/L) is 0.3 mmol/L higher

many metabolic disorders. There are many

than

regulatory

directly-tested-serum

(Table

1).

understanding

the

maintenance

mechanisms

for

of

electrolyte

Potassium levels of serum stored for 2 hours

balance in organisms. Disturbances of these

(4.32 mmol/L) is 0.01 mmol/L higher than 3-

mechanisms lead to electrolyte imbalance,

hours-stored and direct-tested one (4.31

which may be a life-threatening clinical

mmol/L) (Table 1). Chloride levels of both

condition.

serums stored for 2 hours and 3 hours (104

common manifestation of many diseases. All

mmol/L) is 1 mmol/L higher than direct-

electrolyte

tested one (103 mmol/L) (Table 1). In this

comprehensively

statitiscally analysis, a p-value higher than

examination is essential to clarify the clinical

0.05 (> 0.05). It is means that no diffreny was

scenario

observed.

treatment. Most electrolyte imbalances are

imbalance

imbalances

for

should

considered.

effective

and

is

a

be
The

successful

93

Ina. J. Med. Lab. Sci. Tech. 2021; 3(2): 90–98

Electrolyte

Amalia Nurul Fauziah, et al.

low and high sodium, potassium, calcium,

services. This condition will improve the

and magnesium (14).

quality of care and affect the results (16).

Potassium maintains the cardiac rhythm
and

contributes

neuromuscular

abnormal fluid balance in the patient can be

conduction. K level imbalance, indicated by

challenging. The diagnosis of fluid balance

hyperkalemia or hypokalemia, will cause

abnormalities requires the informed and

cardiac arrhythmias and neuromuscular

reasonable interpretation of clinical and

weakness. Chloride (Cl) helps to maintain

laboratory data (17).

electrical neutrality with Na. Cl also

Several pre-analytical variables affect

maintains acid-base balance by buffering H+

electrolyte results, including the type of

equal hydrogen changes and Cl changes to

anticoagulant,

maintain electrical neutrality through the

hemolysis. Hemolysis of blood causes a false

movement of bicarbonate ions (HCO3-).

increase in plasma K results by releasing

Kidney and endocrine disorders are usually

intracellular K. However, grossly hemolyzed

characterized

electrolyte

specimens will affect the analyses of Na and

imbalance. Changes in electrolyte levels are

Cl levels due to a dilutional effect. The

associated with pathological consequences

presence of excess anticoagulants when small

and increased mortality (15).

volumes of blood are collected will similarly

by

plasma

storage

conditions,

and

Analysts use laboratory diagnostic for

cause a dilutional effect and falsely decreased

diagnosis, monitoring, and prognosis in

plasma levels of Na and Cl. Refrigeration of

patients.

the

unseparated whole blood may enhance the

potential to improve patient safety since it

intracellular release of K from erythrocytes

crosses many pathways and organizational

(15).

Laboratory

boundaries.

94

to

Distinguishing between the normal and

medicine has

Clinicians

can

implement

Various studies on the stability of

proactive interventions to highlight high-risk

chemical metabolites, especially sodium,

situations, such as pre-assessment and drug

potassium, and chloride in serums, give

therapy monitoring. Laboratories have a

mixed results. Hedayati et al. (18) revealed

considerable role to play in diagnostic and

that after the first cycle (24 h) at 2 to 8°C,

therapeutic decision-making and monitoring

changes

safety. There are many such examples

potassium, and chloride) were less than 10%.

highlighted in this paper, but increasing the

After serum stored in refrigeration in three

knowledge of the use and abuse of testing,

cycles (72 h). At this moment, serum chloride

and studying the outcomes, should be part of

was changes as 0.4% and statistically

the value-added function of laboratory

significant at the 5% level. Donnelly et

in

all

the analytes

(sodium,

Ina. J. Med. Lab. Sci. Tech. 2021; 3(2): 90–98

Amalia Nurul Fauziah, et al.

al. (19) compared sodium, potassium, and

stability of sodium, potassium, and chloride

chloride levels in serums stored at room

can

temperature (4oC) and -20oC for 48 hours, 14

centrifugation. Na and Cl results are affected

days, and four months. While O'Keane et al.

at 3 hours, but K results are affected at 1 hour.

(20) showed that all metabolites, including

Climatic conditions and uncovered sample

sodium, potassium, and chloride, have the

cups left under the fan for a few hours are

stability of up to 48 hours if stored at a

responsible for this evaporation and falsely

temperature of 4oC. Some researchers

high serum electrolyte values (12). Research

discover that sodium and chloride levels in

conducted in tropical Indonesia gave similar

the serum can be stable for up to 12 hours

results. The effect of long delays in serum

with

rapid

examination for 0, 3, 5, and 7 hours was

centrifugation and storage at 4°C, the

observed by other researchers that performed

electrolytes can be stable for 48 hours (21).

a serum examination of sodium and chloride

These data indicate that changes in these

levels (25). Other researchers discovered that

analytes are not consistent across all cycles

delayed sample-processing of over 2 (two)

and storage temperatures tested (18).

hours did not affect the serum sodium and

serum

separation.

After

change

after

a

few

hours

of

In the cooling process, glycolysis is

chloride level. On the other hand, delayed

inhibited. Thereby Na-K ATPase-depending

sample-processing of more than 2 (two)

power

hours can affect potassium levels (13).

cannot

maintain

its

gradient.

Consequently, intracellular potassium will

According to An et al. (26), Na, K, and

exit the erythrocytes, leading to an increase in

Cl examination samples stored at room

potassium

(22).

temperature will consistently increase over

Furthermore, storing of erythrocytes showed

time, whereas low-temperature storage will

increased potassium leakage, and all these

prevent such changes. The evaporation of

effects increased with increasing storage time

samples can cause an increase in such

(23). Since sodium density is lower than the

metabolites.

chloride (24), there is only one-tenth of

conditions and closed containers or tubes are

sodium in erythrocytes, so serum testing

highly recommended for long-term storage.

delays do not cause sodium leakage into the

This research reveals that the average Na,

levels

in

plasma

serum (13).

Therefore,

cold

sample

K, and Cl levels in all treatments (directly

Various electrolyte results depended on

examined and stored for 2 hours and 3 hours

the temperature conditions of each country.

at a temperature of 4oC) are relatively

Research conducted in tropical countries will

comparable. There was

provide higher temperatures so that the

difference in sodium (p = 0.719), potassium

95

Ina. J. Med. Lab. Sci. Tech. 2021; 3(2): 90–98

no significant

Amalia Nurul Fauziah, et al.

(p = 0.976), or chloride (p = 0.772) levels in

unclear how long the maximum storage time

serums of all treatments, according to

will affect the serum sample's stability. In

statistical tests. The findings are comparable

previous studies by Trisna et al. (13), sample-

to those of Donnelly et al. (19) and O'Keane

processing delays of over 2 hours do not

et al. (20), who discovered that serum can be

affect the results of sodium and chloride

stored at 4 degrees Celsius for up to 48 hours.

examinations,

This discovery indicates that the storage of

delays of more than 2 hours can affect

serum specimens for examination of sodium,

potassium results.

while

sample-processing

potassium, and chloride should pay attention
to the container, conditions, and storage
temperature, making the serum's stability can

CONCLUSIONS
This

study

found

no

significant

difference in Sodium (Na+), Potassium (K+),

last longer (27).
Serum storage in clinical laboratories is

and Chloride (Cl-) levels of the serum with all

still widely used in Indonesia. As a result,

treatments (directly examined or stored for 2

each laboratory's guidelines should state the

hours and 3 hours at 4oC), indicating that

stability of each analyte's storage. The

postponing the serum examination for 3

laboratory

of

hours with various considerations is still

storage

permissible. According to these findings, The

must

Operational

follow

Procedure

standards
for

optimization.

analyst should keep serum specimens for

The researcher should consider the type

electrolyte analysis (Na+, K+ and Cl-) at 4°C

and stability of specimen, anticoagulants,

for a maximum of 3 hours. In previous

preservatives, and containers when storing

studies, sodium and chloride were affected 3

samples for electrolyte analysis. Serum

hours

samples for the study of Na, K and Cl can be

temperature, while potassium results were

stored for 14 days at a temperature of 20-

affected 1 hour after centrifugation at room

25°C. Alternatively, if stored at 4°C, it can

temperature. Further research is needed to

last for 14 days (27).

determine the maximum storage time at 4oC,

This study shows that the storage of
serum for sodium, potassium, and chloride

after

centrifugation

at

room

which can affect the stability of serum
electrolytes.

analysis can be done at a maximum of 3 hours

96

at a temperature of 4oC. The limitation of this

AUTHOR CONTRIBUTIONS

study is the determination of the storage

Amalia

length of serum samples, which is limited to

conceptualization,

only 2 hours and 3 hours. As a result, it is

analysis,

Nurul

Fauziah:

term,

methodology,

formal

investigation,

resources,

data

Ina. J. Med. Lab. Sci. Tech. 2021; 3(2): 90–98

Amalia Nurul Fauziah, et al.

curation, writing-original draft, visualization,
supervision, project administration, funding
acquisition.

M.

Atik

Martsiningsih:

ACKNOWLADGEMENTS
Appreciation goes to the Management of
Laboratory

Unit,

Pratama

Hospital

conceptualization, methodology, validation,

Yogyakarta city, which commits to carry out

writing - review & editing, visualization,

this research successfully.

editing or revision of the manuscript. Budi
Setiawan: conceptualization, methodology,
formal analysis, data curation, writing review & editing, visualization, editing, or

CONFLICT OF INTEREST
The authors declare no conflict of
interest.

manuscript revision.

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