3120 SWEAT CHEK Instruction and Service Manual M2672-2A

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© 2005 Wescor, Inc. All rights reserved. Printed in the United States of America. Wescor, Macroduct, Sweat-Chek, Webster Sweat Inducer and Calibrator are trademarks of Wescor, Inc. Other trade names used in this manual may be trademarks of their respective owners, used here for information only. U.S. Patent Numbers 4,383,529; 4,542,751. U.K. Patent Number 2,116,850. German Patent (DBP) 33 09 273. All information in this manual is subject to change without prior notice.

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section

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INTRODUCTION 1.1 Instrument Description... 1.2 Customer Service... 1.3 Controls and Connections... 1.4 Important User Information...

3 4 5 6

section

2

OPERATING SWEAT•CHEK 2.1 Instrument Preparation... 2.2 Sweat Analysis... 2.3 Cleaning the Conductivity Cell... 2.4 System Operating Checks...

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section

3

INTERPRETATION OF RESULTS 3.1 Background... 3.2 Units of Measurement and Clinical Ranges... 3.3 Conductivity and the CAP Survey Program... 3.4 Conductivity in the Diagnostic Analysis of Sweat... 3.5 Reportable Range and Its Justification... 3.6 References...

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section

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TROUBLESHOOTING AND SERVICE 4.1 Troubleshooting and Service Overview... 4.2 Instrument Calibration... 4.3 Replacing the Conductivity Cell...

29 30 33

APPENDIX A Instrument Specifications...

37

APPENDIX B Accessories, Supplies, and Replacement Parts

...

41

Changing the Voltage Selector...

45

APPENDIX C INDEX... 49 iii

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1.1 Instrument Description

3120

SWEAT• CHEK Sweat Conductivity Analyzer

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1.1 Instrument Description The 3120 SWEAT•CHEK Sweat Conductivity Analyzer provides simple and economical sweat analysis for the laboratory diagnosis of cystic fibrosis. Designed specifically for use with the Wescor Macroduct® Sweat Collector, it can measure the electrolyte concentration of a sweat specimen as small as 6 to 10 microliters. The Analyzer’s flow-through conductivity cell operates at a precisely controlled temperature for improved stability and accuracy. In keeping with established practice, the readout on the digital display is calibrated in mmol/L (equivalent NaCl). The reading obtained represents the molar concentration of sodium chloride in aqueous solution that would exhibit, at the sample temperature, the observed sample conductivity. The conductivity cell is located beneath a recessed cover on the front panel of the instrument, just below the digital display. In the recess of this cover, two short 0.76 mm diameter stainless steel nipples serve as inlet and outlet connections to the cell. For measurement, two short lengths of microbore plastic tubing are slipped over the stainless steel nipples. One of these tubes is from the Macroduct sweat collector and contains the sweat specimen to be analyzed. The other tube serves as the “takeup” tube. During analysis, the sweat specimen is transferred from the Macroduct tube into the takeup tube via the conductivity cell. After the sweat specimen is transferred into the cell, its electrical conductivity is measured, the electrolyte concentration is calculated, and the result appears on the digital display. Complete instructions for this procedure are found in Section 2.

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1.2 Customer Service Wescor is ready to help you resolve any problems with your SWEAT•CHEK Analyzer. If you cannot solve a problem using the procedures in this manual please contact us. Customers within the United States and Canada are encouraged to contact us by telephone. Outside the U.S., many of our authorized dealers offer complete customer service and support. Contact Wescor by mail, telephone, fax or email at the address and numbers listed below. Wescor, Inc 459 South Main Street Logan, Utah 84321-5294 USA TELEPHONE: (435) 752 6011 TOLL FREE: (800) 453 2725 (U.S. and Canada) FAX: (435) 752 4127 E-MAIL: [email protected] WEBSITE: www.wescor.com NOTE: Wescor’s Authorized European Representative for matters relating to the Medical Device Directive is: MT Promedt Consulting GmbH Altenhofstraße 80 D-66386 St. Ingbert, Germany Tel: +49 6894 581020 Fax: +49 6894 581021 email: [email protected] www.mt.procons.com

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1.3 Controls and Connections

DIGITAL DISPLAY

INSTRUMENT FRONT

INLET/OUTLET NIPPLES

WAIT INDICATOR READY INDICATOR CONDUCTIVITY CELL

POWER INDICATOR

INSTRUMENT REAR CALIBRATING TOOL MODEL AND SERIAL NUMBER

POWER CORD RECEPTACLE

POWER SWITCH

CALIBRATION PORT POWER ENTRY MODULE

The power switch is located on the back of the instrument as part of the Power Entry Module. When connected to the proper line voltage and turned ON (I) the power indicator should glow GREEN.

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1.4 Important User Information SPECIFICATION OF SAFE USE: Using this instrument in a manner not specified by Wescor may impair the safety protection designed into the equipment and may lead to injury. SAFE USE ENVIRONMENT: This device has been designed for indoor use only, between 5 and 40 °C, maximum relative humidity 80%, at up to 31 °C. For use at altitudes up to 2000 meters. FUSES: All fuses in this equipment are time-lag (Type T). For use with a Mains Supply voltage of 85 to 264 Volts AC @ 50 to 60 Hz, ±10%. Transient Overvoltage Category II. Pollution Degree 2 in accordance with IEC 664. EXPLANATION OF SYMBOLS FOUND ON EQUIPMENT:

∼ Alternating Current (AC) I

Power On

O

Power Off International Attention Symbol. Calls attention to important information and instructions in the instruction manual.

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2.1 Instrument Preparation

1

The power switch is located on the back panel in the power entry module. Make certain the switch is OFF (0).

2

Plug the female end of the power cord into the power entry module. Note the voltage indicator window. If the voltage does not match the voltage of your power outlet, refer to Appendix C before proceeding.

NOTE: We recommend using a grounded power line surge protector to isolate the instrument from spikes and surges.

3

Plug the male end of the power cord into a grounded power outlet.

4

Turn the power switch on (I). The power indicator should glow GREEN. The display will read zero:

The WAIT indicator glows amber. Within two minutes, it will switch off and the READY indicator will glow green, indicating that the conductivity cell has stabilized at the correct operating temperature. The Analyzer is now ready to accept samples.

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2.1 Instrument Preparation

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5

Attach a length of clean microbore tubing (SS044) to serve as the outlet tube to one of the stainless steel nipples. While either nipple can be used, we suggest that the right hand nipple be used as the outlet.

6

Check calibration before introducing specimen, (see Section 2.4). After calibration (if needed), clean and dry the cell before proceeding with analysis, (see Section 2.3).

7

Attach the tube containing the specimen for analysis to the opposite (we recommend the left) nipple, which will serve as the inlet. See Section 2.2 for complete instructions.

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2.2 Sweat Analysis The Macroduct Sweat Collection System manual provides complete instructions for sweat collection. These should be followed rigorously. Normally, the sweat specimen is introduced directly into the conductivity cell from the Macroduct collection tube. A typical Macroduct sweat collection produces many times the sweat volume needed for analysis. In cases where sweat yield is below average, measurement is possible using 6 to 10 microliters of sweat; but careful and precise technique is mandatory, since positioning of the sample within the cell becomes critical. If the sample volume is insufficient to establish continuity between the electrodes in the conductivity cell (approximately 6 microliters), no measurement will be possible. However, any reading sustained on the digital display for at least a few seconds will be valid. PREVIOUSLY COLLECTED SWEAT OR SWEAT CONTROLS If the sweat specimen has been transferred to a storage cup, or if you wish to inject Calibrator solution (SS-140), sweat control solutions (SS-150), or water into the Analyzer, simply attach a spare take-up tube to the syringe. Position the syringe plunger near mid-point, and carefully withdraw the plunger to bring the specimen into the tube. Use only new, clean tubing that is certified solute-free to avoid measurement errors (tubing supplied by Wescor meets this requirement). Do not aspirate liquid into the syringe body.

NOTE: Handle the sweat specimen with care before analysis to avoid introducing air bubbles into the sweat column. An air bubble in the conductivity cell will prevent measurement.

the end of the specimen tube to the inlet nip1 Connect ple of the conductivity cell (we suggest the left hand nipple). Push tubing “straight on” the nipple.

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2.2 Sweat Analysis CAUTION! Push the tubing STRAIGHT ON to the stainless steel nipples without bending them. Repeated bending will eventually cause the nipple to fracture, requiring replacement of the conductivity cell.

the specimen into the cell by gently moving 2 Transfer the syringe plunger into its barrel. When the liquid column of the specimen makes contact with the cell electrodes, the digital display will rise quickly from its zero reading. Stop injecting the sample at this point, and the sample will rapidly equilibrate to the cell temperature. Moving the liquid column brings cooler liquid into the conductivity cell, briefly producing a lower reading, but the reading quickly stabilizes when motion ceases. In large samples, a slight beginning-to-end conductivity variation is normal. See Section 3.2 to interpret readings.

the liquid column of the specimen loses con3 When tact with the first cell electrode, the reading will fall to zero.

desired, the specimen can be drawn back into the 4 Ifcell to repeat the measurement. If the plunger is moved smoothly and gently, the specimen can be transferred in and out of the conductivity cell for as many measurements as desired. Abrupt, jerky movements of the plunger can separate the liquid column, and the resulting air bubbles will interrupt readings as they pass through the cell.

clean and dry the conductivity cell using the 5 Thoroughly instructions in Section 2.3. 12

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2.3 Cleaning the Conductivity Cell

1

After testing each specimen, rinse the conductivity cell with at least one full take-up tube of deionized water.

2

When all residual salt has been flushed from the cell, the reading on the display reads “000” (with pure water in the cell).

3

Remove water by using the syringe to push air through the cell. After all discernible liquid has been flushed, remove the take-up tube and “pump” the syringe to blow out any remaining micro droplets and dry the cell. Finally, push the syringe plunger completely down to purge remaining droplets of water from the cell. This procedure is necessary to ensure accuracy of any subsequent measurement.

CAUTION! Never allow any liquid to remain in the conductivity cell after measurements are complete. Besides risking a measurement artifact in the next procedure, the instrument can be damaged if it is inadvertently exposed to freezing temperatures such as could occur during transport to a testing site in cold weather. To avoid damage to the cell or other sensitive electronic components, do not expose the instrument to extremes of heat or cold.

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2.4 System Operating Checks SWEAT•CHEK is factory-calibrated and under normal conditions should not require further adjustment. IF THE CELL IS CLEAN AND FREE OF RESIDUAL SALT OR WATER, calibration of the instrument can be checked using a freshly opened NaCl standard solution such as that initially supplied with the instrument. The reading given by the Analyzer should agree with the specified molarity of the standard solution within ± 2 mmol/L. If recalibration becomes necessary refer to Section 4.2.

SWEAT•CHEK has an extremely stable response characteristic that is virtually linear through the critical range from 75 to 110 mmol/L. At extremely low ranges, there will be a slight positive error in the reading, and at extremely high ranges, a slight negative error. These errors will not invalidate the diagnostic result. See Section 3.5.

Check calibration to ascertain that the temperature of the cell is within the correct range and that the electronics are otherwise functioning normally. A reading that agrees with the labeled value of the standard solution indicates correct overall performance to a very high level of confidence. Further testing is not normally necessary. Sweat Controls Normal Appr. 40 mmol/L

High Normal/Equivocal Appr. 70 mmol/L

If you require a CF-positive and/or CF-negative control value, Wescor Sweat Controls (SS-150) provide three levels of control for validating measurements of electrolyte concentration as shown at left:

Abnormal Appr. 130 mmol/L

CAUTION! Push the tubing STRAIGHT ON to the stainless steel nipples without bending them. Repeated bending will eventually cause the nipple to fracture, requiring replacement of the conductivity cell.

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INTERPRETATION OF RESULTS

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3.1 Background

Children afflicted with cystic fibrosis (CF) clearly show elevated electrolyte concentrations in their sweat, compared with the sweat of children unaffected by this disease.1,2 With increasing age, however, the difference between normal and abnormal sweat electrolyte levels becomes less distinct; thus, the borderline and low abnormal results commonly encountered in adults are not indicative of disease. A diagnosis of CF will always be based upon clinical findings and observations, but the “laboratory diagnosis” or “sweat test,” performed properly, provides valuable quantitative corroboration of the physician’s clinical diagnosis. Historically, the “sweat test” was performed without Macroduct and SWEAT•CHEK and has shown a high incidence of both false positive and false negative results, with false positives predominating. The professional literature3,4,5 has been highly critical of various commercial systems that purport to simplify one or more of the three steps in the procedure, i.e. SWEAT INDUCTION, SWEAT COLLECTION and SWEAT ANALYSIS. Most of the errors involved the collection phase of the test. Webster’s comprehensive review of quantitative sweat testing, from the early 1950’s through 1983, identified error factors associated with each of these methods.6 Although numerous sweat testing systems have been marketed, the Cystic Fibrosis Foundation of America has approved only two methods of sweat collection. They are the original pad absorption method of Gibson and Cooke7 and the Wescor Macroduct Sweat Collection System.8,9 The sweat test’s analytical phase was limited to chloride ion assay in laboratories of the early 1950’s. Today, laboratory technologists can choose from a number of alternative analytical methods, including anion assay, cation assay, osmolality, or electrical conductivity. The SWEAT•CHEK Sweat Conductivity Analyzer measures the electrolyte concentration of the specimen by electrical conductivity. 17