RETICULOCYTE METHOD, RBC INDICES

K954594 · Bayer Corp. · GKZ · Aug 23, 1996 · Hematology

Device Facts

• Record ID: K954594
• Device Name: RETICULOCYTE METHOD, RBC INDICES
• Applicant: Bayer Corp.
• Product Code: GKZ · Hematology
• Decision Date: Aug 23, 1996
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 864.5220
• Device Class: Class 2

Device Story

Technicon H-3 RTC/RTX is an automated hematology analyzer for reticulocyte counting and RBC index determination. Device processes human blood samples; utilizes flow cytometry-based methodology to measure reticulocytes and RBC parameters. System provides quantitative outputs for % reticulocytes, absolute reticulocyte count, and various RBC indices (MCV, CHCM, CH, RDW, HDW). Used in clinical laboratory settings by trained laboratory personnel. Results assist clinicians in assessing erythropoietic activity and diagnosing hematological conditions. Device performance is validated against manual NCCLS reference methods.

Clinical Evidence

Bench testing only. Accuracy evaluated against NCCLS manual new methylene blue method (n=196 samples from healthy and hospital donors). Reticulocyte count correlation: r=0.97 (% retic), r=0.93 (abs retic). RBC indices compared to H-3 CBC/Diff mode showed high correlation (r=0.937-0.990). Precision assessed via 25 replicates; CVs reported for reticulocyte parameters (12.1-12.7%) and RBC indices (0.3-8.1%). Linearity confirmed 0-26% reticulocytes. No carryover observed. Sample stability tested 15-90 minutes.

Technological Characteristics

Automated hematology analyzer utilizing flow cytometry. Measures reticulocytes and RBC indices. Includes specific incubation requirements (15-90 minutes for reticulocytes; 15-20 minutes for most RBC indices). Connectivity and software architecture not specified. Sterilization not applicable.

Indications for Use

Indicated for the automated counting of reticulocytes and determination of red blood cell indices in human blood samples, including those from healthy donors and hospital patients with red cell abnormalities.

Regulatory Classification

Identification

An automated differential cell counter is a device used to identify one or more of the formed elements of the blood. The device may also have the capability to flag, count, or classify immature or abnormal hematopoietic cells of the blood, bone marrow, or other body fluids. These devices may combine an electronic particle counting method, optical method, or a flow cytometric method utilizing monoclonal CD (cluster designation) markers. The device includes accessory CD markers.

Special Controls

*Classification.* Class II (special controls). The special control for this device is the FDA document entitled “Class II Special Controls Guidance Document: Premarket Notifications for Automated Differential Cell Counters for Immature or Abnormal Blood Cells; Final Guidance for Industry and FDA.”

Reference Devices

• Technicon H-2 system
• NCCLS proposed standard for reticulocyte counting

Submission Summary (Full Text)

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AUG 23 1996
Attachment 4
SUMMARY OF SAFETY AND EFFECTIVENESS
K954594

# METHOD PERFORMANCE CHARACTERISTICS

The following is a summary of performance characteristics obtained from evaluations of the Technicon H-3 RTC/RTX reticulocyte method. The values shown in this section are point estimates of performance which can be expected from the method. Similar evaluations may produce slightly different results depending on the characteristics of the donor population.

# ACCURACY

## Reticulocyte Count

Accuracy of the Technicon H-3 RTC/RTX reticulocyte method was evaluated by comparison to the NCCLS⁵ proposed standard for reticulocyte counting using new methylene blue. Fifty samples were obtained from apparently healthy donors and forty-eight samples were obtained from hospital patients including patients with known red cell abnormalities. Each sample was counted independently by two technologists using the NCCLS method and was assayed in duplicate on a Technicon H-3 for a total sample size of n = 196. Reference absolute counts were obtained from the technologist % reticulocyte result and an RBC count from a Technicon H-2 system. The test results appear in the table below.

| Parameter | r | Slope | Intercept | Sy x | Reference Mean | H-3 Mean | Range of Samples |
| --- | --- | --- | --- | --- | --- | --- | --- |
| % retic | 0.97 | 0.93 | 0.0 | 0.56 | 2.0 | 1.9 | 0.2 to 26.2 |
| abs retic (10⁹/L) | 0.93 | 0.86 | 6.4 | 22.6 | 84.9 | 79.1 | 7.4 to 552.8 |

Due to the substantial error associated with the manual counting technique⁶, laboratories performing similar accuracy evaluations may obtain incorrect least squares regression coefficients when the range of samples is small⁷. In this event, the coefficients can be corrected by averaging manual results from 4 or more technologists, or by calculating the regression coefficients using a method derived by Deming⁸.

# RBC Indices

Accuracy of the Technicon H-3 RTC/RTX reticulocyte method RBC indices was evaluated by comparison to the RBC indices obtained from the H-3 RBC/platelet and hemoglobin methods (CBC/Diff mode) in the experiment described above (n = 196). Accuracy of MCV, CHCM, RDW, and HDW was evaluated by comparison to the identical parameter obtained from the RBC/platelet method. The accuracy of CH was evaluated by comparison to MCH which is calculated from the RBC count and hemoglobin measurement.

| Parameter | r | Slope | Intercept | Sy x | Mean in CBC/Diff Mode | Mean in Reticulocyte Mode | Bias |
| --- | --- | --- | --- | --- | --- | --- | --- |
| MCV | 0.974 | 0.88 | 10.0 | 1.0 | 84.8 | 84.7 | -0.1 |
| CHCM | 0.988 | 1.06 | -1.6 | 0.7 | 33.1 | 33.5 | 0.4 |
| CH | 0.980 | 0.95 | 2.0 | 0.6 | 27.5 | 28.0 | 0.5 |
| RDW | 0.937 | 1.06 | -0.8 | 0.5 | 15.7 | 15.8 | 0.1 |
| HDW | 0.990 | 1.13 | -0.25 | 0.14 | 2.79 | 2.90 | 0.11 |

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SUMMARY OF SAFETY AND EFFECTIVENESS

# WITHIN RUN PRECISION CHARACTERISTICS

Within run precision of the reticulocyte method was tested by 25 replicate assays performed for each of 5 samples obtained from apparently healthy donors. The average result, which represents typical performance, appears in the table below.

Table 4-6 REPLICATE PRECISION

| Parameter | Mean | SD | CV (%) |
| --- | --- | --- | --- |
| Retic (%) | 1.1 | 0.14 | 12.7 |
| Abs Retic (10^{9} cells/L) | 52.2 | 6.3 | 12.1 |
| MCV (fL) | 90.5 | 0.44 | 0.5 |
| MCVr (fL) | 110.8 | 2.1 | 1.9 |
| CHCM (g/dL) | 32.3 | 0.20 | 0.6 |
| CHCMr (g/dL) | 27.7 | 0.5 | 1.5 |
| CH (pg) | 28.6 | 0.08 | 0.3 |
| CHr (pg) | 29.9 | 0.5 | 1.3 |
| RDW (%) | 13.2 | 0.09 | 0.7 |
| RDWr (%) | 14.8 | 1.2 | 8.1 |
| HDW (g/dL) | 2.59 | 0.05 | 1.9 |
| HDWr (g/dL) | 3.04 | 0.22 | 7.2 |
| HHDW (pg) | 3.40 | 0.02 | 0.6 |
| HHDWr (pg) | 3.84 | 0.28 | 7.3 |

# LINEARITY

The linearity of the % reticulocyte count was tested by making serial dilutions of a human pool prepared to obtain a high reticulocyte count. The results from this study indicate that the response is linear from 0% to 26% reticulocytes.

# CARRYOVER

Carryover of the reticulocyte method was measured using high level and low level human pools. No detectable carryover was observed for reticulocyte counts.

# PREPARED SAMPLE STABILITY

## Reticulocyte Count

Prepared sample stability over the claimed range of 15 to 90 minutes was tested by assaying 15 prepared samples obtained from apparently healthy donors from 15 to 90 minutes at 15 minute intervals. The test results indicate that all samples were within ±0.5% of the % reticulocyte recovery obtained at 30 minutes.

## RBC Indices

With the exception of CH and CHr, the RBC indices are not stable over the entire incubation period. When reporting results for RBC indices other than CH and CHr, the samples should incubate for at least 15 minutes, but not longer than 20 minutes. CH and CHr are stable over the entire 15 to 90 minute incubation period.

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