Verification of the Sediplus® S 2000 NX Blood
Sedimentation Monitor
Simple and hygienic determination of up to
40 sedimentation rates within one hour
Müller-Drebelhof C.1, Dietrich S.1, Will D.1
1

SARSTEDT AG & Co. KG, Research & Development, Nümbrecht, Germany

Abstract
The erythrocyte sedimentation rate (ESR) is usually measured automatically in the clinical routine. The accuracy andprecision of automated measurements must be verified by the manufacturer for the in vitro diagnostics market. In this study,
the successor model for the determination of ESR, the Sediplus® S 2000 NX, was verified by comparative measurements
in comparison to the current accepted market standard, the Sediplus® S 2000. The verification study was conductedaccording to the recommendations of CLSI H02-A05. Comparative measurements were performed on 64 blood samples
with ESR values in a range of 2 - 84 mm/h Westergren. The mean values found [mm Westergren / 1 h] were almost
identical (31.3 mm/h with Sediplus® S 2000 vs. 31.2 mm/h with Sediplus® S 2000 NX; p-value = 0.689). Subsequently,
the precision (SD max. 1.6 mm/h with the Sediplus® S 2000 vs. SD max. 2.1 mm/h with the Sediplus® S 2000 NX) of thetwo devices was determined by multiple measurements. Again, we confirmed very good agreement. The high accuracy
and the associated compliance with clinical acceptance criteria as well as the high precision of the Sediplus® S 2000 NX’s
ESR values confirm the conformity of the device for the in vitro diagnostics market.

Introduction
The determination of the erythrocyte sedimentation rate
(ESR), was first described in 1921 by Dr R. Fahraeus
and Dr A. Westergren (Fahraeus, 1921; Westergren,1921).1 It quickly became a common screening test for
acute phase proteins and chronic diseases worldwide(Westergren, 1926). Its ease of determination makes
this nonspecific disease indicator a widely used test forscreening and surveillance in cases of unclear disease
to even monitoring the success of treatment for certain
diseases.
During blood sedimentation, erythrocytes sediment
due to their higher density compared to blood plasma.2
Due to the negatively charged erythrocyte surface (zeta
potential), neighboring cells repel each other when they
are below a certain distance and remain in suspension. In
the case of inflammatory diseases, the increased content
of acute phase proteins such as fibrinogen in the plasmapresumably leads to a lowering of the zeta potential andthus to a faster sinking of the erythrocytes.3
To determine the ESR, blood anticoagulated withcitrate solution is filled into a standardized column(sedimentation pipette) and after one hour the distancetravelled by the descended erythrocytes is read off in
mm. For decades, the S-Sedivette® has been a popular invitro diagnostic tool in clinical laboratories. In addition
to its function as a closed blood collection system, theS-Sedivette® also serves as a sample vessel for blood

sedimentation. The S-Sedivette® differs significantly
in geometry and preparation from the Westergren
sedimentation pipette (Fig.2). This simplified handlingand made it safer for the user. However, this led to
the fact that the BSG scale is now not linear as with
the Westergren sedimentation pipette, but has a nonlinear scale that is increasingly compressed towards
the bottom. In order to further simplify the BSG
determination, the Sediplus® S 2000 was developed
over time for the automated reading of the BSG.
The Sediplus® S 2000 NX, as verified here, complies
with the latest directive for in vitro diagnostic medical
devices (2017/746/EU) (Fig. 1). The requirements forelectrical safety and electromagnetic compatibility
were tested according to DIN EN 61010 and DIN EN
61326. The intuitive operation of the device via thetouch display allows the measurement to be started
quickly. The BSG values are then output via the display
and optionally via the network interface (HL7). This
allows the values to be transferred to the laboratory’s
own computer system (LIS). Up to 40 measurements
can be carried out in parallel.
The measuring principle for determining the ESR isbased on infrared (IR) transmission. The S-Sedivettes
are inserted vertically into the openings intended forthis purpose. A measuring table mounted on the device
is moved linearly up and down during the measuring
process. At the same time, each individual S-Sedivette®
is illuminated by an infrared measuring beam during

Verification of the Sediplus® S 2000 NX Blood
Sedimentation Monitor
the movement of the measuring table. This beamhits phototransistors integrated within the measuringtable, which detect the boundary between supernatant(plasma) and sedimented erythrocytes by light intensity.
The height of the border between supernatant anderythrocyte sediment is measured by counting the stepsof the stepper motor inside the device. This sampling
process takes place for each sample (S-Sedivette®) atuser-defined times (0 h, ½ h and 1 h or 0 h, 1 h and 2 h). A
software-supported conversion into Westergren values[mm/h] takes place on the basis of the determined heightin millimetres and the specified time. The verification of
the software-supported conversion was already carriedout on the predecessor model Sediplus® S 2000.4
In this study, comparative measurements against
the accepted market standard (gold standard), theSediplus® S 2000, were therefore performed to verify
the automated ESR determination with the Sediplus®
S 2000 NX.

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Verification of the Sediplus® S 2000 NX Blood
Sedimentation Monitor

Material & Methods

Results••

Part 1: Comparative BSG measurements on the two
Sediplus® devices, the accepted market standard S 2000
and the new S 2000 NX to be verified.

••

Sediplus® S 2000 NX (follow-up model)
accepted market standard (gold standard) Sediplus®
S 2000Comparative BSG measurements on both devices(part 1)
Multiple measurements to determine the precisionin the series (part 2)

The verification of the Sediplus® S 2000 NX wascarried out in accordance with CLSI H02-A05.5 For thispurpose, 64 samples with ESR values over the entire
measuring range were measured comparatively on both
ESR devices. The different ESR values of blood fromhealthy donors were obtained by adding gelatine into
the citrate solution.6 Immediately before starting themeasurements, the samples were thoroughly mixedagain by inverting them five times.

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The data obtained (Tab. 1) were first tested for significant
differences using paired T-tests.
Tab. 1: Measured ESR [mm Westergren] after 1 h, on the
two Sediplus® devices

To determine the precision, 10 repeat measurements ofa sample from each of the four quartiles of the entire
measuring range were carried out. For this purpose, 10
identical samples were measured in parallel on bothdevices.

Fig. 1: Sediplus® S 2000 NX; optimized measuring instrument forthe determination of blood sedimentation in S-Sedivettes; with touch
display; allows parallel determination of up to 40 samples within
one hourFig. 2: S-Sedivette®; the only validated closed blood collection
system for the Sediplus® S 2000 NX

The mean values over all samples are almost identical forthe two devices with 31.3 mm/h vs. 31.2 mm/h and do notdiffer significantly (p = 0.689).
For further comparison, a regression analysis according to
Passing-Bablok was carried out (Fig.3).

Verification of the Sediplus® S 2000 NX Blood
Sedimentation Monitor

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Verification of the Sediplus® S 2000 NX Blood
Sedimentation Monitor

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differences (mean ESR: 31.3 mm/h vs. 31.2 mm/h) wereobserved between the two devices (p-value = 0.689) (Tab. 1).
Consistent with this, the correlation analysis carried out
according to Passing-Bablok also showed no significant
difference in the measured values. The 95 % confidence
intervals enclose the value of 1 for the slope and 0 for
the intercept.(Fig. 3). Furthermore, the measured valuesof both devices were visually examined for systematicabnormalities using a Bland Altman difference plot. Again,
no systematic deviation between the two devices could beobserved (Fig. 4).

Fig. 4: The difference plot analysis according to Bland-Altman does notindicate any systematic measurement errors due to BSG measurementwith the Sediplus® S 2000 NX.

The measuring range tested here was limited by the gelatine
additive method (max. 84 mm/h). However, tests with TestSedivettes also showed equivalent results up to ESR valuesof 116 mm/h.

The differences between the pairs of values are apparently
evenly distributed upwards and downwards over themeasuring range. There are no systematic differences
between the readings of the two devices.

The accuracy of the measured values obtained on the
Sediplus® S 2000 NX was thus confirmed over the entire
measuring range up to 116 mm.

Part 2: Determining the precision in the series
Fig. 3: Correlation according to Passing-Bablok, 1-h ESR values using
Sediplus® S 2000 vs. Sediplus® S 2000 NX

The measured values of both devices are shown in Fig. 3.
The maximum possible measuring range due to gelatine
additives was well covered by the different samples. The
dashed line represents the ideal straight line, the red line
the Passing Bablok regression line, which here almost
corresponds to the ideal (slope: 0.984; intercept: 0.377). The
dotted lines represent the lower and upper 95 % confidence
intervals. Since the slopes of the confidence interval limits
enclose the value of 1 and for the intercept the value of0, the measured values from both devices are assessed as
not significantly different according to CLSI H02-A05.
The systems (Sediplus® S 2000 / Sediplus® S 2000 NX
in combination with the S-Sedivette®) can technicallymeasure ESR values up to 116 mm, but the range of values
with the method carried out here to simulate artificially
increased ESR (gelatin additives) is experimentally
exhausted at 84 mm. Outside the measurement range
tested here, equivalent data as described above wereobtained with blood sedimentation up to 116 mm using
Test-Sedivettes (Sedivettes filled with non-transparent
plastic) (data not shown). The accuracy of the measured
values obtained on the Sediplus® S 2000 NX was thus
confirmed over the entire measuring range up to 116 mm.
Furthermore, a Bland-Altman diagram was used to visuallycheck whether systematic differences exist between themeasured values from the S 2000 and S 2000 NX (Fig.4).

Tab. 2: Multiple measurements of identically prepared
donor blood samples on both Sediplus® devices

The precision measurements were made at four different
positions in the measuring range. The standard deviation(SD) was determined here as a measure of the precisionin the series. Maximum SD deviations of 1.6 mm for the
S 2000 and 2.1 mm for the S 2000 NX were measured.

Discussion
In this study, the new Sediplus® S 2000 NX blood
sedimentation measurement device should be verified for thein vitro diagnostics market in accordance with the Directive
on In Vitro Diagnostic Medical Devices (2017/746/EU).
For this purpose, the requirements of electrical safety
and electromagnetic compatibility according to DIN EN
61010 and DIN EN 61326 were tested. The suitability ofthe measuring function was confirmed in accordance with
CLSI H02-A05.
To verify the measuring function, comparative ESR
determinations were carried out with the predecessor model
Sediplus® S 2000. The comparative ESR measurementsof 64 blood samples showed a very high correlation
between the two devices. In the paired T-test, no significant

In the second step, the “precision in the series” wasdetermined on both devices. The ESR was determined inparallel on 20 identical samples. The ESR measurements
were taken at four different positions with the widest possible
distribution over the entire measuring range. Both devices
showed comparably good precision with a maximum
standard deviation of absolutely 2.1 mm/h Westergren for
the S 2000 NX. This is a maximum of 0.5 mm/h Westergren
above the maximum imprecision (SD) of the S 2000. In
addition to the mechanical-physical imprecision, the small
variances in blood sample preparation also contributeto the maximum imprecision. The minimal mean value
differences in the determination of the imprecision can also
be explained, among other things, by test delays and thus
already incipient blood sedimentation until the start of themeasurements. However, these minimal differences are notclinically relevant.

Conclusion
The data of the study conducted here show a very highcorrelation of the measured ESR values determined with
the new Sediplus® S 2000 NX compared to the acceptedmarket standard, the Sediplus® S 2000. In addition to thehigh accuracy of the measured values of both devices,comparably good “precisions in series” were determinedon both devices. This means that the Sediplus® S 2000 NX
blood sedimentation meter is equivalent to the Sediplus® S
2000 blood sedimentation meter (accepted market standard)in terms of accuracy and precision and thus confirms
conformity for blood sedimentation measurements for thein vitro diagnostics market.

Verification of the Sediplus® S 2000 NX Blood
Sedimentation Monitor
The Sediplus® S 2000 NX is thus verified in accordancewith the latest directive for in vitro diagnostic medical
devices (2017/746/EU).

DisclosureThis work was funded by Sarstedt AG & Co. KG. The
authors are employees of Sarstedt AG & Co. KG.

References

J. M. Jou et al. ICSH review of the measurement oferythrocyte sedimentation rate, Int. Jnl. Lab. Hem. 2011,
33, 125-132
2
Lothar Thomas, Labor und Diagnose, Online–
Ausgabe, 10. Auflage 2020
3
J. Fest et al: Erythrocyte sedimentation rate as an
1

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independent prognostic marker for mortality: aprospective population-based cohort study, Journal ofInternal Medicine, 2019, 285; 341-348
4Comparative Study SARSTEDT Blood Sedimentation
Systems
https://www.sarstedt.com/fileadmin/user_upload/
Mediacenter/Studien/Blood_Sedimentation_
Systems/20_376_0000_200_BSG_Studie_1120.pdf
5
CLSI H02-A5, Procedures for Erythrocyte Sedimentation
Rate Test; Approved Standard – Fifth Edition, May 2011, 28
6
R. Sümpelmann, R. Zander, Gelatine schützt Erythrozyten
in vitro und in vivo vor mechanischer Belastung,
Anästhesiol Intensivmed Notfallmed Schmerzther,
2001:36

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