MODIFICATION TO CARBON DIOXIDE-L3K ASSAY, CAT. NOS. 299-30, 299-17, 299-50, 299-80 AND 299-12

K042362 · Diagnostic Chemicals , Ltd. · KHS · Dec 27, 2004 · Clinical Chemistry

Device Facts

• Record ID: K042362
• Device Name: MODIFICATION TO CARBON DIOXIDE-L3K ASSAY, CAT. NOS. 299-30, 299-17, 299-50, 299-80 AND 299-12
• Applicant: Diagnostic Chemicals , Ltd.
• Product Code: KHS · Clinical Chemistry
• Decision Date: Dec 27, 2004
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 862.1160
• Device Class: Class 2

Indications for Use

For the quantitative determination of carbon dioxide in serum and plasma. For IN VITRO diagnostic use.

Device Story

Carbon Dioxide-L3K Assay is an in vitro diagnostic reagent kit for measuring CO2 levels in serum and plasma. It replaces traditional manometric, volumetric, or titrimetric techniques with an enzymatic method. The assay utilizes phosphoenolpyruvate carboxylase (PEPC) and a stabilized NADH analog to catalyze a reaction proportional to the CO2 concentration in the sample. Designed for use on routine laboratory instrumentation, the assay provides quantitative results to clinicians for assessing respiratory acidosis or alkalosis. The procedure simplifies laboratory workflow by eliminating cumbersome acid-liberation steps, facilitating faster diagnostic turnaround for patients with suspected respiratory or metabolic CO2 imbalances.

Clinical Evidence

No clinical data. Performance established via bench testing: precision (CV 1.1-1.7%), linearity (2.9-50 mmol/L), and interference studies (icterus, lipemia, hemoglobin). Method comparison (n=45) against a predicate method yielded a correlation coefficient of 0.9861. Matrix recovery studies confirmed plasma equivalence to serum (96.9% vs 97.9% recovery).

Technological Characteristics

Enzymatic assay; liquid reagents containing buffer (pH 7.6), PEP, PEPC, malate dehydrogenase, NADH analog, activators, stabilizers, surfactant, and preservative. Requires instrumentation with temperature control (±0.5°C) and absorbance sensitivity of 0.001 at 405 or 415nm. Standardized via NCCLS EP6-P and EP9-A.

Indications for Use

Indicated for the quantitative determination of carbon dioxide in serum and plasma for in vitro diagnostic use in clinical laboratory settings.

Regulatory Classification

Identification

A bicarbonate/carbon dioxide test system is a device intended to measure bicarbonate/carbon dioxide in plasma, serum, and whole blood. Bicarbonate/carbon dioxide measurements are used in the diagnosis and treatment of numerous potentially serious disorders associated with changes in body acid-base balance.

Submission Summary (Full Text)

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510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION
DECISION SUMMARY
DEVICE ONLY TEMPLATE

A. 510(k) Number:
k042362

B. Purpose for Submission:
Add plasma as an acceptable sample matrix

C. Analyte:
Carbon Dioxide

D. Type of Test:
Quantitative

E. Applicant:
Diagnostic Chemicals Limited

F. Proprietary and Established Names:
Carbon Dioxide-L3K Assay

G. Regulatory Information:
1. Regulation section:
21 CFR §862.1160 Bicarbonate/carbon dioxide test system,
(Enzymatic, Carbon Dioxide)
2. Classification:
Class II
3. Product Code:
KHS
4. Panel:
75 - Chemistry

H. Intended Use:
1. Intended use(s):
See Indications for Use below.
2. Indication(s) for use:
Carbon Dioxide – L3K Assay is indicated for the quantitative determination of carbon dioxide in serum and plasma. For in vitro diagnostic use.
Elevated blood CO₂ is almost synonymous with respiratory acidosis. The later is restricted to clinical conditions with a primary increase in carbon dioxide in the inspired air or increased metabolic production of carbon dioxide.

Decreased blood CO₂ is almost synonymous with respiratory alkalosis. The later is restricted to clinical conditions with primary decrease in carbon dioxide which can result from increased pulmonary ventilation due to mechanical ventilation or stimulation of the respiratory center.

Classic techniques for the measurement of carbon dioxide (CO₂) involve the addition of acid to liberate the carbon dioxide and the measurement of carbon dioxide thus released by either manometric, volumetric, or titrimetric

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techniques. These procedures are both time consuming and cumbersome. The DCL Carbon Dioxide-L3K assay is an enzymatic procedure, employing phosphoenolpyruvate (PEPC) and a stabilized NAD analog, which is easy to use and applicable to routine laboratory instrumentation.

3. Special condition for use statement(s): For in vitro diagnostic use only
4. Special instrument Requirements: Any instrument with temperature control of $\pm 0.5^{\circ}\mathrm{C}$ that is capable of reading absorbance with a sensitivity of 0.001 at 405 or $415\mathrm{nm}$ .

I. Device Description: Carbon Dioxide reagent is a solution containing buffer (pH 7.6 at $25^{\circ}\mathrm{C}$ ), 12.5 mmol/L PEP, >400 U/L PEPC (microbial), >4100 U/L malate dehydrogenase (mammalian), 0.6 mmol/L NADH analog, activators, stabilizers, a surfactant, and a preservative.

J. Substantial Equivalence Information:

1. Predicate device name(s): Carbon Dioxide-L3K Assay
2. Predicate K number(s): k990754
3. Comparison with predicate:

| Similarities | | |
| --- | --- | --- |
| Item | Device | Predicate |
| Intended Use | Same | Same |
| Test Type | Enzymatic | Enzymatic |
| Reagents | Liquid reagents | Liquid reagents |
| Differences | | |
| Item | Device | Predicate |
| Sample type | Serum & Plasma | Serum |

K. Standard/Guidance Document Referenced (if applicable):

NCCLS EP6-P – Evaluation of the Linearity of Quantitative Analytical Methods
NCCLS EP9-A – Method Comparison and Bias Estimation Using Patient Samples

L. Test Principle:

Carbon Dioxide – L3K Assay is based on enzymatic reactions. The specimen is first alkalinized to convert $\mathrm{CO}_{2}$ and carbonic acid to $\mathrm{HCO}_{3}^{-}$ . By catalysis of phosphoenolpyruvate carboxylase (PEPC), the reaction of bicarbonate and phosphoenolpyruvate (PEP) produces oxalacetate and phosphate. Malate dehydrogenase catalyzes the reduction of oxalacetate to malate with the simultaneous oxidation of reduced nicotinamide adenine dinucleotide (NADH) to $\mathrm{NAD}^{+}$ . Decrease

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in absorbance of NADH at $415\mathrm{nm}$ is proportional to the total $\mathrm{CO}_{2}$ content in the sample.

# M. Performance Characteristics (if/when applicable):

# 1. Analytical performance:

a. Precision/Reproducibility:

Within run precision was established by assaying two control sera twenty times each.

| Carbon Dioxide | Mean Mmol/L (mEq/L) | Standard Deviation Mmol/L (mEq/L) | Coefficient of Variation % |
| --- | --- | --- | --- |
| Serum 1 | 13.5 | 0.18 | 1.3 |
| Serum 2 | 24.0 | 0.40 | 1.7 |

Run to run precision was established by assaying two control sera in triplicate in each of 5 runs.

| Carbon Dioxide | Mean Mmol/L (mEq/L) | Standard Deviation Mmol/L (mEq/L) | Coefficient of Variation % |
| --- | --- | --- | --- |
| Serum 1 | 14.1 | 0.24 | 1.7 |
| Serum 2 | 24.8 | 0.27 | 1.1 |

b. Linearity/assay reportable range:

Linearity studies were designed using NCCLS EP6-P, Evaluation of the Linearity of Quantitative Analytical Methods. The linearity of the procedure described is $50\mathrm{mmol / L}$ (mEq/L). The lower limit of detection of the procedure described is $2.9\mathrm{mmol / L}$ (mEq/L). These data result in a reportable range of 2.9-50 mmol/L (2.9-50 mEq/L).

c. Traceability (controls, calibrators, or method):

No traceability was provided.

A carbon dioxide standard is not included with the reagents, however one should be used as directed to calibrate the procedure.

d. Detection limit:

Lower Limit of Detection (LLD) is defined as the concentration that can be differentiated from zero using a predetermined confidence interval. Ten samples of saline were analyzed and results were calculated using LLD= Mean + 3 SD with LLD= 0.767 mmol/L.

e. Analytical specificity:

Interferences from icterus, lipemia, and hemolysis were evaluated for this carbon dioxide method on a Hitachi 717 analyzer using a significance criterion of $>10\%$ variance from the control. No significant lipemia interference was found at

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Intralipid levels from 0-1000 mg/dL (0-3000 mg/dL triglycerides) in a 24.6 mmol/L (mEq/L) carbon dioxide sample. No significant icteric interference was found at bilirubin levels from 0-40 mg/dL (0-684 mg/dL triglycerides) in a 27.1 mmol/L (mEq/L) carbon dioxide sample.

Hemoglobin levels of 0-155 mmol/L (0-1000 mg/dL) were studied with acceptable results to a level of 93 umol/L (600 mg/dL). At a hemoglobin level of 93 umol/L (600 mg/dL), a 10.3% positive interference was displayed in a 26.3 mmol/L (mEq/L) carbon dioxide sample. A summary of the influence of drugs on clinical tests is referenced within the package insert

f. Assay cut-off:
Not applicable

2. Comparison studies:

a. Method comparison with predicate device:
Accuracy was evaluated based on NCCLS Protocol EP9-A2. The performance of this method (y) on a Hitachi was compared with performance of a similar carbon dioxide method (x) on a Cobas Mira. Forty-five serum samples ranging from 15.4-43.7 mmol/L (mEq/L) gave a correlation coefficient of 0.9861. Linear regression analysis gave the following equation:
This method = 1.00 (reference method) - 0.42 mmol/L (mEq/L).

b. Matrix comparison:
Recovery Study for CO2 in Serum and Plasma:
This study was conducted to provide supporting evidence for the acceptability of using plasma samples with the DCL CO2 L3K assay. The data presented below demonstrate an equivalent performance when sodium bicarbonate is spiked into serum and plasma samples.

Serum Recovery:
Control Sample - 0.5 mL serum from patient A + 0.025 mL saline
Test Sample I - 0.5 mL serum from patient A + 0.025 mL 100 mmol/L CO2 standard
Test Sample II - 0.5 mL serum from patient A + 0.025 mL 300 mmol/L CO2 standard

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| Sample | Concentration Measured (mmol/L) | Concentration Added (mmol/L) | Concentration Recovered (mmol/L) | Recovery (%) |
| --- | --- | --- | --- | --- |
| Control | 23.7 | | | |
| Test I | 28.3 | 4.8 | 4.7 | 97.9 |
| Test II | 37.7 | 14.3 | 14.0 | 97.9 |
| Average Recovery in Serum | | | | 97.9% |

Plasma Recovery:

Control Sample - 0.5 mL plasma from patient A + 0.025 mL saline

Test Sample I - 0.5 mL plasma from patient A + 0.025 mL 100mmol/L CO2 standard

Test Sample II - 0.5 mL plasma from patient A + 0.025 mL 300 mmol/L CO2 standard

| Sample | Concentration Measured (mmol/L) | Concentration Added (mmol/L) | Concentration Recovered (mmol/L) | Recovery (%) |
| --- | --- | --- | --- | --- |
| Control | 25.0 | | | |
| Test I | 29.7 | 4.8 | 4.7 | 97.9 |
| Test II | 38.7 | 14.3 | 13.7 | 95.8 |
| Average Recovery in Serum | | | | 96.9% |

The acceptable criteria for the recovery studies was set to Recovery = 95 – 105%. Therefore all recovery data are acceptable and plasma is considered to be equivalent to serum.

3. Clinical studies:
a. Clinical sensitivity: Not applicable
b. Clinical specificity: Not applicable
c. Other clinical supportive data (when a and b are not applicable) None

4. Clinical cut-off: Not applicable

5. Expected values/Reference range: Values of 22-29 mmol/L (mEq/L) are reported in Tietz, NW. (Editor), Textbook of Clinical Chemistry, W.B. Saunders Co., Philadelphia (1986). These values are suggested guidelines. The applicant recommends that each laboratory establish the reference range for the area in which it is located.

N. Conclusion: The submitted information in this premarket notification is complete and supports a substantial equivalence decision.