Instrumentation for free light chain immunoassays
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27 |
SECTION 5 - Practical aspects of free light chain testing |
| Instrumentation for free light chain immunoassays |
Introduction
Immunoassays for serum free light chains (sFLCs) (Freelite™) are available for the majority of nephelometric and turbidimetric laboratory instruments. They all utilise latex-enhancement to allow detection of FLCs at low concentrations. Nephelometers and turbidimeters have similar levels of sensitivity and precision but instruments vary in their ability to handle samples, clean reaction cuvettes, identify antigen excess, etc. Smaller laboratories tend to use nephelometers that are dedicated to protein measurements but sample handling is relatively slow. Such instruments may not have “open” channels, so technical assistance is frequently required to implement the FLC tests.
Large laboratories tend to use multifunctional chemistry instruments that analyse proteins turbidimetrically. These instruments are usually more precise and stable than dedicated protein analysers and may be more “user-friendly” for new assay implementation. However, some external assistance is usually required to ensure proper running of the assays and interpretation of results.
A comparison of the various attributes of 8 different instruments is shown in Table 27.1 [1]. These assessments were made at the Binding Site production laboratory and because of their extensive experience the results are equivalent to those obtained in an expert laboratory. Throughput was tested by measuring 20 normal serum samples (requiring no re-measurement) and 20 multiple myeloma (MM) samples (requiring multiple remeasurements). These were run separately so that each instrument’s ability to make automatic redilutions could be isolated from its basic throughput. The hands-on time, e.g. manual dilutions, was also recorded. Total precision (n=100) was assessed, and the availability of antigen excess protection was also documented. Instrument reliability was assessed by calculating the average number of breakdowns per unit, per year requiring engineer intervention. Finally, overall performance was assessed by awarding marks from 0 – 3 for each category, apart from 0 or 1 for antigen excess detection.
Basic sample throughput was similar for all instruments but the BNII and ProSpec were affected by longer assay times. Instruments offering multiple automatic redilutions showed faster throughput for MM sera with the Modular P and SPAPLUS showing the best processing speed, with only a few minutes hands-on required. Precision was good overall, although the best precision was seen with instruments using disposable cuvettes (Integra 400/800 and BN ProSpec). Antigen excess protection was only available on the SPAPLUS, MININEPHPLUS and Integra 400/800, giving reassurance that high samples are not mis-reported. Where reliability was concerned, the Beckman Coulter AU 400 and SPAPLUS performed best, with less than a single breakdown per unit, per year. Overall performance was best for the Integra, SPAPLUS and Beckman Coulter AU 400.
Inevitably, there are occasional assay related “issues” that lead to customer questions or complaints. Analysis of The Binding Site database has showed that approximately 50% of problems were related to inadequate maintenance of the analysers or incorrect parameter programming (Figure 4.17). About 20% were due to problems with calibrators and 15% were related to samples behaving in a non-linear manner. The precision values shown in the tables for each instrument are those found at Binding Site laboratories. If customer attained precision figures are significantly worse, then the instrument or the programming are probably at fault. It should be noted that the majority of complaints have been restricted to two instruments. This is largely because they have been more widely used. Exact information on the performance of the assays and their implementation is contained in the package inserts (also see Chapter 26). Measuring ranges may change slightly with different batches. In addition, for several of the clinical chemistry analysers the FLC assay comes with batch specific technical range limits which must be applied with each new batch of reagents.
| Beckman
IMMAGE®
| Binding Site
SPAPLUS
| COBAS Integra®
400*
| Roche Hitachi
Modular P*
| Beckman Coulter
AU®400
| Siemens
ADVIA®1650*
| Siemens
BNTMII
| Siemens
BN ProSpec®
| |
|---|---|---|---|---|---|---|---|---|
| Sample redilution** | None | 1 | 3 | 1 | 1 | 1 | 2 | 2 |
| 20 Normal samples | 40 mins | 37 mins | 33 mins | 29 mins | 36 mins | 18 mins | 52 mins | 52 mins |
| 20 MM samples | 84 mins | 68 mins | 75 mins | 51 mins | 71 mins | 106 mins | 127 mins | 172 mins |
| Hands-on time | 21 mins | 10 mins | 5 mins | 5 mins | 15 mins | 14 mins | 0 mins | 10 mins |
| Kappa precision | 2.7% | 4.1% | 1.8% | 6.3% | 2.5% | 4.5% | 4.8% | 1.6% |
| Lambda precision | 2.7% | 3.9% | 1.2% | 5.4% | 2.2% | 3.1% | 4.7% | 1.3% |
| Antigen excess | No | Yes | Yes | No | No | No | No | No |
| Breakdown unit/year | 5 | 0.2 | 1 | 6 | 0 | 6 | 1.4 | 6 |
| Overall performance | 12/22 | 16/22 | 20/22 | 13/22 | 16/22 | 12/22 | 14/22 | 14/22 |
Table 27.1. Comparison of sFLC assays (Freelite™) on eight different laboratory instruments. *Other compatible instrument models are available but there is no data. ** 1: single auto redilution, 2: multiple auto redilutions, -3: multiple manually ordered redilutions. Marks from 0-3 were awarded for each category apart from 0 for 1 for antigen excess capability. 20 samples were tested for each parameter.
27.1. Beckman Coulter AU® (400, 640, 2700 and 5400)
The Beckman Coulter chemistry analysers use turbidimetry for the measurement of plasma proteins. All have similar hardware and software but vary in their sample handling capacity. The instruments are open and can be programmed by the user. For the FLC assays, 6 pre-diluted standards are provided. The standard sample dilution is 1/10, sample results outside this range are automatically re-measured at 1/100 or 1/5, while off-line dilutions are required for higher concentrations. Results correlate well with other FLC immunoassays and precision is good (Table 27.2) [2][3].
At present, no specific technical issues have been encountered and comparison with other instruments shows impressive reliability (Table 27.1). Fogging of the glass cuvettes with the latex reagent is a potential problem. This can be prevented by adding a W2 wash with 1% Decon 90 before the normal weekly W2 wash programme.
| Serum κ FLC | Serum λ FLC | |
| Range at 1/10 | 6.0-150.0mg/L | 6.0-150.0mg/L |
| Sensitivity at 1/5 | 3.0 mg/L | 3.0 mg/L |
| Assay time | 8 min | 8 min |
| Precision: within-run | 2.0% at 22.1mg/L | 1.6% at 31.4mg/L |
| 1.2% at 40.8mg/L | 0.8% at 66.1mg/L | |
| 1.9% at 153.3mg/L | 6.8% at 183.1mg/L | |
| Precision: between-run | 5.8% at 22.2mg/L | 5.4% at 29.6mg/L |
| 5.2% at 41.4mg/L | 4.9% at 62.9mg/L | |
| 6.0% at 135.4mg/L | 4.5% at 177.8mg/L |
Table 27.2. Assay performance on the Beckamn Coulter AU® 400 analysers.
27.2. Beckman Coulter IMMAGE® and IMMAGE® 800
The IMMAGE can be used as either a rate nephelometer or as a rate turbidimeter that measure plasma proteins by homogeneous immunoassay. In the case of the FLC assays the latter function is used. The instrument has two basic modes of operation; a fully automated “Beckman” mode, controlled by the manufacturer and a “user-defined” reagent mode. The latter allows assays to be developed by individual laboratories.
The Binding Site provides FLC kits for use in ‘user-defined’ mode. Each contains a preprepared, six level calibrator set, controls, κ or λ latex reagents and product information. Support is usually required for setting up the assays and some disposable components and buffers are required from Beckman Coulter.
The assays use serum samples diluted to 1/10 and the instrument can be programmed to analyse samples at 1/5 if the result is lower than the initial measuring range. Offline dilutions of 1/25 and 1/500 may be required for higher concentrations. The 1/10 dilutions cover the FLC concentrations found in most samples (Table 27.3) [4][5][6].
Assay trouble shooting
- Cuvette fogging: Latex particles accumulate on the cuvettes so they must be changed regularly (every 1,200 Freelite tests).
- Washer probe: This needs particular attention. It must be clean, free from corrosion and correctly aligned.
- Syringes and buffer lines: Check there is no leakage or air bubbles.
- Buffers: The No 1 system diluent must be used.
| Serum κ FLC | Serum λ FLC | |
| Range at 1/10 | 6.0-180.0mg/L | 4.8-162.0mg/L |
| Sensitivity at 1/5 | 3.0mg/L | 2.4mg/L |
| Assay time | 10 min | 10 min |
| Precision: within-run | 8.1% at 10.7mg/L | 2.2% at 13.1mg/L |
| 5.4% at 17.7mg/L | 2.0% at 25.5mg/L | |
| 4% at 147.2mg/L | 6.8% at 138.2mg/L | |
| Precision: between-run | 15% at 9.3mg/L | 7.2% at 11.9mg/L |
| 5.8% at 27.8mg/L | 7.2% at 28.0mg/L | |
| 7.2% at 111.9mg/L | 11.7% at 190.9mg/L |
Table 27.3. Assay performance on the Beckman Coulter IMMAGE®.
27.3. Binding Site MININEPHPLUS™
This is a small, manual nephelometer designed for sFLC analysis. The calibration curves are stored on magnetic swipe-cards. Once loaded into the instrument's memory, curve validity is confirmed by assaying control samples. Patient samples are analysed individually by semi-automated addition of reagents into cuvettes within the instrument. The assays show good linearity, identify antigen excess, have good agreement with the Siemens BNII and are fast (Table 27.4). The instrument may find use in laboratories with low work loads (<10 samples per day) or when the cost of a larger instrument cannot be justified.
| Serum κ FLC | Serum λ FLC | |
| Range at 1/20 | 3.0-72.4mg/L | 4.9-98.3mg/L |
| Sensitivity at 1/20 | 3.0mg/L | 4.9mg/L |
| Assay time | 5 min | 5 min |
| Precision: within-run | 7.3% at 55.82mg/L | 5.1% at 80.54mg/L |
| 5.7% at 18.67mg/L | 3.9% at 29.42mg/L | |
| 4.9% at 4.79mg/L | 3.2% at 7.62mg/L | |
| Precision: between-run | 6.8% at 55.82mg/L | 6.7% at 80.54mg/L |
| 5.7% at 18.67mg/L | 3.8% at 29.42mg/L | |
| 5.0% at 4.79mg/L | 7.4% at 7.62mg/L |
Table 27.4. Assay performance on the the Binding Site MININEPHPLUS.
27.4. Binding Site SPAPLUS bench-top analyser
The instrument is an automated, random access turbidimeter with host interface capability, barcoded sample identification and reagent management systems. Precision is maintained through a combination of acid/alkali cuvette washing and an innovative reaction cuvette mixing system. Air pressure is used in place of stirrers to mix the reaction mixture in a U shaped cuvette. No physical contact is made with the reaction mixture, thereby removing any possibility of carry-over on a stirrer. Calibration curves are made from calibrator sets and validated by assay of control fluids supplied with the kits. Samples are initially measured at the standard programmed sample dilution and if out of range, the instrument automatically re-measures the samples at the appropriate alternative dilutions. All dilutions are made with the instrument’s pipetting system which is capable of dilutions between 1/10 and 1/100. An antigen excess protection function is available. The instrument has a good overall performance compared with other analysers (Tables 27.1 and 27.5) and provides good throughput for myeloma samples in spite of its relatively small size [7][8][9].
| Serum κ FLC | Serum λ FLC | |
| Range at 1/10 | 4.0-180.0mg/L | 4.5-165.0mg/L |
| Sensitivity at 1/1 | 0.4mg/L | 0.5mg/L |
| Assay time | 15 min | 15 min |
| Precision: within-run | 3.3% at 7.2mg/L | 3.4% at 10.4mg/L |
| 1.6% at 35.7mg/L | 2.4% at 35.1mg/L | |
| 1.8% at 123.8mg/L | 2.0% at 142.1mg/L | |
| Precision: between-run | 4.2% at 7.2mg/L | 2.2% at 10.4mg/L |
| 1.9% at 35.7mg/L | 0.0% at 35.1mg/L | |
| 2.3% at 123.8mg/L | 2.4% at 142.1mg/L |
Table 27.5. Assay performance on the Binding Site SPAPLUS.
27.5. Radim Delta™
This is a medium-sized, fully automated bench-top nephelometer, with similar characteristics and performance to the Siemens BNII (Table 27.6). The instrument produces calibration curves from a single calibration fluid [10]. Samples with concentrations of FLCs outside the initial measuring range are automatically re-diluted by the instrument.
| Serum κ FLC | Serum λ FLC | |
| Range at 1/100 | 5.9-190.0mg/L | 5.0-160.0mg/L |
| Sensitivity at 1/5 | 0.3 mg/L | 0.25 mg/L |
| Assay time | 18 min | 18 min |
| Precision: within-run | 7.1% at 8.8mg/L | 4.3% at 15.5mg/L |
| 2.3% at 41.0mg/L | 2.0% at 75.2mg/L | |
| 7.7% at 143.6mg/L | 4.1% at 202.8mg/L | |
| Precision: between-run | 8.2% at 7.2mg/L | 5.3% at 13.1mg/L |
| 7.8% at 40.05mg/L | 5.2% at 47.6mg/L | |
| 7.0% at 144.8mg/L | 6.4% at 143.5mg/L |
Table 27.6. Assay performance on the Radim Delta.
27.6. Roche Cobas® c501 automated analyser
The c501 is part of the cobas 6000 range of instruments intended to replace Roche’s Modular and Integra analysers. This is a random access, turbidimetric analyser using end-point measurements. The instrument features ultrasonic, contact-free stirring. Most parameter channels are dedicated to Roche assays, however parameters for Binding Site FLC channels can be downloaded by the user from the Roche database. Single-vial calibrators are used that are diluted automatically to generate the calibration curves. Starting sample dilutions are 1/5 for κ assays and 1/8 for λ assays. The instrument can be programmed to carry out a single, automatic re-dilution when samples are out of range. Further dilutions for very high samples must be made off-line. Results show a good correlation with the Dade Behring BNII (Table 27.7) [11].
| Serum κ FLC | Serum λ FLC | |
| Range 1/5 (κ); 1/8 (λ) | 3.7-56.2mg/L | 5.6-74.8mg/L |
| Sensitivity (neat) | 0.8 mg/L | 0.7 mg/L |
| Assay time | 10 min | 10 min |
| Precision: within-run | 1.4% at 5.6mg/L | 4.1% at 7.7mg/L |
| 2.5% at 18.5mg/L | 5.5% at 27.3mg/L | |
| 1.7% at 41.1mg/L | 2.8% at 60.3mg/L | |
| Precision: between-run | 7.2% at 5.8mg/L | 10% at 8.0mg/L |
| 7.0% at 19.8mg/L | 3.6% at 28.6mg/L | |
| 2.6% at 41.4mg/L | 2.3% at 63.3mg/L |
Table 27.7. Assay performance on the Roche Cobas® c501.
27.7. Roche Cobas Integra® (400, 400 plus & 800) automated analyser
The Integra 400 is a random access, bench-top turbidimetric analyser using end-point measurement. Although it is a closed system, Binding Site FLC channels are provided as part of the standard menu and can be loaded from a TAS/TASU disc provided by Roche. Single-vial calibrators are used that are diluted automatically to generate the calibration curves. Starting sample dilutions are 1/10 for κ assays and 1/8 for λ assays. Samples outside of the measuring range can be manually selected for on-board redilution and re-measurement. The range of on-board dilution factors is broader on the integra 400 (and 400 plus) than most biochemistry instruments, but very high samples may still require off-line dilution. Use of disposable cuvettes results in precision that is superior to many analysers and it gives the best overall performance (Tables 27.1 and 27.8) [12]. FLC assays are required to be run in batch mode to avoid carry-over from Roche chemistries.
| Serum κ FLC | Serum λ FLC | |
| Range 1/10 (κ); 1/8 (λ) | 2.9-127.0mg/L | 5.2-139.0mg/L |
| Sensitivity (neat) | 0.6mg/L | 1.3mg/L |
| Assay time | 10 min | 10 min |
| Precision: within-run | 5.8% at 6.0mg/L | 2.3% at 7.7mg/L |
| 2.1% at 18.7mg/L | 0.7% at 27.0mg/L | |
| 1.4% at 95.6mg/L | 0.7% at 99.2mg/L | |
| Precision: between-run | 2.7% at 6.0mg/L | 2.5% at 7.7mg/L |
| 2.7% at 18.7mg/L | 0.8% at 27.0mg/L | |
| 1.8% at 95.6mg/L | 0.7% at 99.2mg/L |
Table 27.8. Assay performance on the Roche Cobas Integra 400.
27.8. Roche Hitachi 911/912/917 and Modular P
These instruments measure serum proteins by turbidimetry. Most parameter channels are dedicated to Roche assays but a few can be used with other manufacturers’ products. Single-vial calibrator fluids are used that are diluted automatically to generate the calibration curves [13][14]. The starting sample dilutions are 1/5 for κ assays and 1/8 for λ assays. The instruments can be programmed to automatically re-dilute samples when results are outside the range of the calibration curve (Table 27.9). Very high samples must be diluted off-line. Results show a good correlation with the Siemens BNII.
Assay trouble-shooting The following issues need to be considered with the Modular P:
- Ensure correct settings for the parameters and technical limits. These change with each batch of kits.
- Add an additional "joker-labelled" open channel reagent bottle with saline for diluent.
- If the sodium hydroxide wash buffer bottle is empty, cuvettes become turbid and an "OVER" error message appears.
- If tolerance limits have been exceeded after the water wash, a "CELL" error message appears.
- Wait until the calibrator rack has cleared the pipetting area before loading new controls. This ensures that the new curve information is allocated to the correct samples.
| Serum κ FLC | Serum λ FLC | |
| Range at 1/5 (κ), 1/8 (λ) | 3.7-56.2mg/L | 5.6-74.8 mg/L |
| Sensitivity (neat) | 0.8 mg/L | 0.7 mg/L |
| Assay time | 10 min | 10 min |
| Precision: within-run | 8.0% at 8.2mg/L | 3.7% at 10.7mg/L |
| 3.7% at 30.0mg/L | 2.6% at 42.8 mg/L | |
| 3.0% at 48.9mg/L | 3.5% at 57.4mg/L | |
| Precision: between-run | 7.3% at 6.7mg/L | 9.5% at 11.9mg/L |
| 4.1% at 18.2mg/L | 6.8% at 29.1mg/L | |
| 5.7% at 35.3mg/L | 6.3% at 55.4mg/L |
Table 27.9. Assay performance on the Roche Modular P.
27.9. Siemens ADVIA® 1650, 1800, 2400
The ADVIA series are turbidimetric, floor standing instruments of varying size and throughput, with the old 1650 being replaced by the 1800 model. The software system is open and parameter set-up can be carried out by the user. However, due to its complexity, assistance from the Binding Site may be required. All the instruments feature an optional rack handling system with separate dilution and reaction cuvettes to improve throughput. The starting sample dilutions are 1/5 for κ assays and 1/8 for λ assays and if out of range, the instrument automatically re-measures the samples at a higher or lower dilution [15][16][17]. Because repeat values are only checked and flagged using the range for the standard dilution, all repeat samples should also be checked manually (against the measuring range for the repeated dilution) to ensure valid results. The instrument is fast for normal samples (Tables 27.1). It is linear across the measuring range, has good sensitivity and curve stability and shows good intra-run and inter-run precision (Table 27.10).
| Serum κ FLC | Serum λ FLC | |
| Range at 1/5 (κ), 1/8 (λ) | 3.7-56.2mg/L | 5.6-74.8mg/L |
| Sensitivity (neat) | 0.75mg/L | 0.70mg/L |
| Assay time | 15 min | 15 min |
| Precision: within-run | 6.5% at 9.4mg/L | 6.3% at 9.7mg/L |
| 2.7% at 17.7mg/L | 6.4% at 23.0mg/L | |
| 2.3% at 40.7mg/L | 1.8% at 73.3mg/L | |
| Precision: between-run | 5.0% at 9.6mg/L | 7.1% at 11.2mg/L |
| 1.9% at 18.2mg/L | 2.9% at 24.0mg/L | |
| 2.6% at 40.7mg/L | 3.0% at 77.1mg/L |
Table 27.10. Assay performance on the Siemens (Bayer) ADVIA 1650.
27.10. Siemens BN™II
The BNII is a nephelometer designed for measuring plasma proteins by homogeneous immunoassays. The instrument can be programmed for non-Siemens assays using a software key from the company's engineers. Once programmed, the FLC assays run in a similar manner to other protein tests. A single calibrator fluid is automatically diluted to form a calibration curve. The initial sample dilution is 1/100 with automatic dilution of samples that are outside the calibration range (Table 27.11) [18][19][20][21].
Assay trouble-shooting If the assay is performing poorly the following issues should be considered and an engineer may be needed for assistance:
- Wash system (wash shoe, alignment and tubing). Problems with these components may lead to liquid remaining in the bottom of the cuvettes after cleaning. This may lead to carry-over problems in subsequent assays causing dilution errors and variable results. If fluid remains in the cuvettes after laundering, a service engineer should assess the wash system.
- Syringes. Fluid leakage or excessive air in the syringes and buffer lines.
- Programming. The assays require software programming with a service key (dongle). Check carefully for correct parameter programming before the engineer departs.
- Leaking three-way valves. N-Reaction buffer used in many of the assays may leak across the three-way valve into the FLC assays. This leads to loss of curve reproducibility and poor assay precision (particularly at the low end of the curve). If this occurs the syringes should be primed with N-Diluent prior to running the assays. Avoid running assays that use N-Reaction buffer alongside the FLC assays until after the valve has been replaced.
| Serum κ FLC | Serum λ FLC | |
| Range at 1/100 | 5.9-190.0mg/L | 5.0-160.0mg/L |
| Sensitivity at 1/5 | 0.30mg/L | 0.25mg/L |
| Assay time | 18 min | 18 min |
| Precision: within-run | 3.1% at 13.6mg/L | 8.4% at 15.1mg/L |
| 4.8% at 32.8mg/L | 5.2% at 21.9mg/L | |
| 4.2% at 51.1mg/L | 4.8% at 71.8mg/L | |
| Precision: between-run | 6.3% at 12.0mg/L | 8.1% at 18.4mg/L |
| 8.4% at 32.2mg/L | 4.7% at 24.2mg/L | |
| 7.4% at 54.7mg/L | 7.5% at 71.7mg/L |
Table 27.11. Assay performance on the Siemens BNII.
27.13. Siemens BN ProSpec®
This nephelometric instrument is available in some markets in an 'open-mode', or can be opened for sFLC assays by the Dade Behring engineers with a software programme called “Assay Builder”. Precision of the instrument is good, in part, because of the use of disposable cuvettes (Table 27.12) [21].
| Serum κ FLC | Serum λ FLC | |
| Range at 1/100 | 6.0-190.0mg/L | 8.0-260.0mg/L |
| Sensitivity at 1/5 | 0.30mg/L | 0.40mg/L |
| Assay time | 18 min | 18 min |
| Precision: within-run | 4.0% at 16.0mg/L | 2.0% at 25.0mg/L |
| 6.0% at 30.0mg/L | 3.0% at 56.0mg/L | |
| 4.2% at 51.0mg/L | 4.8% at 72.0mg/L | |
| Precision: between-run | 4.0% at 25.0mg/L | 2.0% at 22.0mg/L |
| 2.0% at 36.0mg/L | 1.0% at 44.0mg/L | |
| 4.0% at 80.0mg/L | 1.0% at 141.0mg/L |
Table 27.12. Assay performance on the Siemens BN ProSpec.
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References
- ↑ Showell PJ, Lynch EA, Mitchell F, Mead GP, Bradwell AR. Comparison of serum free immunoglobulin light-chain assays on eight Nephelometric/Turbidimetric analysers. Clin Chem 2008;54:C92a
- ↑ Showell PJ, Matters DJ, Long JM, Carr-Smith HD, Bradwell AR. Evaluation of latex-enhanced turbidimetric reagents for measuring free immunoglobulin light-chains on the Olympus AU400. Clin Chem 2003;49:D55a
- ↑ Ramasamy I. Serum free light chain analysis in B-cell dyscrasias. Ann Clin Lab Sci 2007;37:291–4 PMID: 17709698
- ↑ Tate JR, Gill D, Cobcroft R, Hickman PE. Practical considerations for the measurement of free light chains in serum. Clin Chem 2003;49:1252–7 PMID: 12881439
- ↑ Harris J, Tang LX, Showell PJ, Carr-Smith HD, Drew R, Bradwell AR. Assays for immunoglobulin free light chains in serum on the Beckman IMMAGE™. Clin Chem 2000;46:A180a
- ↑ Ong S, Sethi S. Assessment of free light chain assasy in serum on the Beckman ImmageTM. Clin Chem 2003;49:D59a.
- ↑ Showell PJ, Hutchison CA, Cockwell P, Harding S, Mead GP, Mitchell F, Bradwell AR. Correlation of FREELITE and Cystatin C in Chronic Kidney Disease on The Binding Site SPAPLUS bench-top analyser. Clin Chem 2007;53:C82a
- ↑ Showell PJ, Scurvin M, Chnivimba A, Carr-Smith HC, Bradwell AR. Evaluation of latex-enhanced turbidimetric reagents for measuring free immunoglobulin light-chains on The Binding Site automated analyser. Clin Chem 2006;52:E41a
- ↑ Marionneaux S, Zetlmeisl M, van Hoeven KH, Fagan D, Elkins B, Shulman S. Analytical evaluation of kappa and lambda serum free light chains on The Binding Site SPAPLUS. Clin Chem 2008;54:C79a
- ↑ Showell PJ, Lynch EA, Carr-Smith H, Bradwell AR. Evaluation of latex-enhanced nephelometric reagents for measuring free immunoglobulin light-chains on the Radim Delta. Clin Chem 2004;50:C40a
- ↑ Lynch EA, Showell PJ, Johnson-Brett B, Mead GP, Bradwell AR. Evaluation of latex-enhanced turbidimetric reagents for measuring free immunoglobulin light chains on the Roche cobas c501. Clin Chem 2008;54:C93a
- ↑ Showell PJ, Lynch EA, Johnson-Brett B, Mead G, Bradwell AR. Evaluation of latex-enhanced turbidimetric reagents for measuring free immunoglobulin light-chains on the Roche COBAS Integra 400 automated analyser. Clin Chem 2007;53:C18a
- ↑ Showell PJ, Long JM, Carr-Smith HC, Bradwell AR. Evaluation of latex-enhanced turbidimetric reagents for measuring free immunoglobulin light-chains on the Hitachi 911/912. Clin Chem 2002;48:A66a
- ↑ Overton J, Goodier D, Carr-Smith HD, Bradwell A. Evaluation of latex-enhanced turbidimetric reagents for measuring free immunoglobulin light-chains on the Roche Modular P. Clin Chem 2003;49:D60a
- ↑ Wands C, Powell M, Jupp R. The development of serum free light chain immunoassay on Bayer Advia. Proceedings of ACB National Meeting 2003;2:3a
- ↑ Carr-Smith HD, Harland B, Anderson J, Overton J, Wieringa G, Bradwell AR. Evaluation of latex-enhanced turbidimetric reagents for measuring free immunoglobulin light chains on the Bayer Advia 1650. Clin Chem 2004;50:A82;C44a
- ↑ Higgins T, Cho C, Dayton J. Evaluation of a method to measure free light chains using Bayer Advia 1650 chemistry analyzer. Clin Chem Lab Med 2007;45:M316a
- ↑ Bradwell AR, Carr-Smith HD, Mead GP, Tang LX, Showell PJ, Drayson MT, Drew R. Highly sensitive, automated immunoassay for immunoglobulin free light chains in serum and urine. Clin Chem 2001;47:673-80 PMID: 11274017
- ↑ Carr-Smith HD. Production Director, Binding Site Group Ltd. Personal communication 2008.
- ↑ Katzmann JA, Abraham RS, Dispenzieri A, Lust JA, Kyle RA. Diagnostic performance of quantitative kappa and lambda free light chain assays in clinical practice. Clin Chem 2005;51:878–81 PMID: 15774572
- ↑ 21.0 21.1 Showell PJ, Lynch EA, Overton J, Carr-Smith HD, Bradwell AR. Evaluation of latex-enhanced nephelometric reagents for measuring free immunoglobulin light chains on the Dade Behring ProSpec. Clin Chem 2005;51:B38a
