POCT TPR 30027

/ Version: 1 / Page 1 of 11
TITLE: I-STATE INR/PT PROCEDURE / Reviewed Date: 1-21-2013

This procedure applies to:

Stanford Hospital & Clinics (SHC)

Stanford Outpatient Eye Surgery Center Lab

1.0PURPOSE

The I-Stat PT/INR test is a quantitative whole blood determination of the prothrombin time used for monitoring oral anticoagulant (warfarin) therapy using fresh capillary or venous whole blood samples. The I-STAT PT/INR test is not intended for evaluating individual factor deficiencies. The test determines the time required for complete activation of the extrinsic pathway of the coagulation cascade when initiated (activated) with a thromoboplastin. In traditional prothrombin time tests, complete activation is indicated when activated thrombin converts fibrinogen to fibrin and extensive or localized clots are detected mechanically or optically. The I-STAT PT/INR test is similar except that the endpoint is indicated by the conversion of a thrombin substrate other than fibrinogen. An electrochemical sensor is used to detect this conversion.

The added thrombin substrate is H-D-phenylalanyl-pipecolyl-arginine-p-amino-p methoxydiphenylamine, which has the structure:

Phenylalanine-Pipecolic acid-Arginine--NH-C6H4-NH-C6H4-OCH3

Thrombin cleaves the amide bond at the carboxy terminus of the arginine residue (denoted by the two dashes) because the bond structurally resembles the thrombin-cleaved amide linkage in fibrinogen. The product of the thrombin-substrate reaction is the electrochemically inert tripeptide Phenylalanyl-Pipecolyl-Arginine and the electroactive compound NH3+-C6H4-NH-C6H4-OCH3. A formation of the electroactive compound is detected amperometrically and the timeof detection is measured.

System Overview:

  • I-STAT cartridge: Each I-STAT PT/INR Cartridge provides a sample collection chamber, sensors to detect the coagulation endpoint and and dry reagents necessary to initiate and allow coagulation. Inert matrix components and reagents are coated on a section of the sensor channel and include the following reactive ingredients: Recombinant Tissue Thromboplastin, Heparinase I, Thrombin Substrate.
  • I-STAT analyzer: A portable hand-held instrument into which the blood filled cartridge is inserted for analysis. The I-STAT has a built-in mechanical system, which monitors the electrical interconnecting system, the calibrant delivery system, the sample delivery system and the thermal control system (37°C).
  • Docking Station: Electronically sends data from the I-STAT to the lab, and uploads information from the lab control center.
  • Central Data System (Lab): A dedicated desktop computer, called the I-STAT Central Data Station (CDS), provides the primary information management capabilities for the I-STAT system. IR Link connected to any hand held analyzer allows for transmission of patient records from the test site to the CDS. PT/INR results can be stored, edited, and transferred to the laboratory information system.

2. SPECIMEN REQUIREMENTS

Follow established patient identification procedures including checking the patient Medical Record Number and name.

A.Fingerstick Puncture

1. Preparation of patient: Stimulate blood flow by having the patient wash or soak the fingertip in warm water. Clean fingertip with alcohol wipe; allow fingertip to dry before performing capillary puncture.

2. Only fresh capillary or venous whole blood is suitable. A large, hanging (second) drop of blood, about 20 microliters (L), is needed.

3. Use a safety lancet device that provides a deep puncture so blood flows freely. Puncture in a non-callused area of the fingertip. Wipe away the first drop of blood with sterile gauze. Apply the second large, hanging drop of blood immediately (within 10 seconds) to the application well.

B. Because the test is performed at the patient’s examination room on fresh whole blood, the blood sample is identified by the patient’s Registration label on patient log. Manual logging and identification of patient’s Medical Record number (MRN), Account #, and Name may be necessary prior to blood collection when patient Registration label is not available.

C. Testing personnel should log in date, time of blood collection, ICD9 #, meter #, INR/PT result and operator I.D.

D. Unacceptable specimens

1. Blood collected in glass tubes or syringes, or in tubes containing anticoagulants, is unacceptable. Plasma or serum cannot be used.

2. Blood taken from the same arm receiving intravenous infusion is not acceptable.

3. Blood which is not free flowing due to poor capillary or venipuncture technique is not acceptable as it may produce erroneous results.

4. Blood which is clotted or semi-clotted

5. Blood obtained by repeat sampling from the same fingerstick puncture.

2.0 EQUIPMENT/MATERIAL/AND REAGENTS

  1. I-STAT Analyzer:
  2. I-STAT PT/INR Cartridges
  3. Store the main supply at 2-8°C.
  4. Do not allow cartridges to freeze or return cartridges to be refrigerated after they have been at room temperature.
  5. Record the date on the cartridge box or individual package when it is removed from refrigeration. Cartridges may be at room temp(18-30°C) for 14 days. Cartridges should not be removed from the pouch until time of use.
  1. Controls:
  2. I-STAT PT Level 1 and Level 2 controls
  3. Plastic disposable Transfer Pipettes

3.0QUALITY CONTROL PROCEDURE

The Internal and External simulators produce low and high signals, which mimic the

electrical characteristics of the signals produced by the sensors. The software in the analyzer measure these low and high signals and checks the measurements against predetermined thresholds and indicates their acceptability to the user via a PASS/FAIL message.

  1. Internal Electronic Simulator
  2. The Internal Electronic Simulator is programmed in each I-STAT analyzer and runs automatically every 8 hours of patient testing.
  3. After every 8 hours of patient testing, the Internal Electronic Simulator test cycle is automatically activated when a cartridge is inserted.
  4. If the analyzer passes the simulator test, the cartridge test cycle proceeds. If not, the simulator is tested again.
  5. Reinserting the same cartridge immediately after the FAIL message will activate the simulator test again.
  6. If the analyzer fails again, call the POCT Dept. at 4-8934 for troubleshooting advice. The analyzer disables patient testing if Internal Simulator failed.
  1. External Electronic Simulator (EQC)
  2. Store at room temperature and protect contact pads from contamination by placing the Electron Simulator in its protective case.
  3. External Electronic simulator is used when the I-Stat instrument prompts “SIMULATOR RUN REQUIRED”.
  4. Insertion of the External Electronic Simulator activates the cartridge test cycle which measures both low and high electronic signals. Proceed with patient testing when test “PASSED” ,message is displayed.
  5. If “FAIL” message is displayed, re-insert the external Electronic Simulator to activate to activate the test cycle.
  6. If QC needs to be repeated, sensors can be cleaned gently with an alcohol wipe.
  7. Contact the POCT department at 4-8934 if EQC fails repeatedly. The analyzer disables patient testing when the External Electronic Simulator fails.
  1. Liquid Quality Control (LQC)
  2. Run I-STAT PT Level 1 and Level 2 once a month on the unit and with each new shipment of cartridges in the POC Department.
  3. Set up I-STAT analyzer in the Quality Test, Control, I-STAT cartridge mode up to the screen that shows “Insert Cartridge” before preparing the control. This will hold for 5 minutes.
  4. Control preparation:
  5. After a 45 minute RT equilibration, remove the cap and stopper from one lyophilized human plasma control vial and remove the cap from one vial of Calcium chloride reconstituting fluid.
  6. Pour the entire contents of the liquid vial into the lyophilized plasma control vial. Place the stopper back in the reconstituted control vial, sealing the vial appropriately so that the contents do not leak or spill out
  7. Allow the vial to sit at room temp. for 1 minute.
  8. Mix the contents of the vial by swirling gently for 1 minute, then inverting slowly for 30 seconds
  9. Using a plastic transfer pipette or syringe with no anticoagulant, immediately transfer the solution from the vial into the PT cartridge.
  10. Immediately seal the cartridge and insert it into the analyzer.
  11. Record result and go to the next level, if appropriate.

5.0 INSTRUMENT CALIBRATION

See appendix for method; calibration verification only performed in POCT Lab

6.0 PATIENT SAMPLE PROCEDURE

1. Preparation of I-STAT analyzer : Press On button; Menu; select I-Stat Cartridge; and stop at Insert Cartridge.

  1. Remove cartridge from pouch and set flat on the counter near the analyzer.
  2. Prepare finger for sample according to A1-3.
  3. Touch the drop of blood against the bottom of the sample well. Once in contact with the sample well, the blood will be drawn into the cartridge.
  4. Apply sample until it reaches the fill mark indicated on the cartridge.
  5. Fold the sample closure over the sample well, pressing the rounded end of the closure until it clamps into place.

Note: to further simplify the sample application into the test cartridge, bring the cartridge to the finger for easer application. Do ensure that the instrument remains on a flat vibration-free surface. Also, this cartridge is designed to accept a sample between 20 and 45μ. A single drop of blood will typically be within this range.

  1. Insert cartridge into the analyzer
  2. Follow prompts entering Operator ID, 8 digit Patient I.D. number, and sample type, then page forward. Field 2 may be used to discard the result by entering 8 and paging forward.
  3. PT and INR results will be displayed, and results are entered on the logsheet.
  4. Results will be sent to the data management system in POCT when the meter is docked.
  5. If results appear inconsistent with the clinical assessment, recollect the sample and repeat the test with another cartridge.

7.0 SAFETY WARNINGS

A.Because of the hazardous nature of handling blood products, disposable gloves are used when collecting specimens, performing testing procedures and cleaning testing equipment.

B.Gloves are removed and hands washed thoroughly with soap and water after completing the test procedure and before handling equipment not related to the procedure.

C.Universal precautions are observed for all blood specimens. Blood samples are handled at Biosafety Level 2 as recommended for any potentially infectious material in the Centers for Disease Control / National Institutes of Health manual, Biosafety in Microbiological and Biomedical Laboratories, 1988. The exterior of the meter is cleaned and disinfected with a solution of 10 % households’ bleach if contaminated with blood.

D.Use fingerstick lancet with safety device for one time use. Dispose of used lancet and blood contaminated products in Biohazard container. Follow the SHC Laboratory Phlebotomy Procedure for correct fingerstick specimen collection.

EUse Biohazard sharp container and waste container to dispose of blood contaminated products.

F.Notify your department manger and Employee Health immediately if you are stuck accidentally by a used lancet.

G.The meter should be cleaned (including after each patient use) with Sani-Cloth wipes.Do not get cleaning solution into the meter. Dry thoroughly with paper towel or malfunctions of the meter may occur.

1. Do not immerse meter in any liquid.

2. Use ground power cord for connecting meter to electrical outlet.

3.Dispose of used batteries in accordance to StanfordHospital and Clinics Policy.

8.0 RESULT EXAMPLE

Results are displayed in International Normalized Ratio (INR) in units and PT seconds.

9.0 COMPUTATIONS OF INR RESULTS

The PT/INR result is reported as an International Normalized Ratio (INR) and, optionally, in seconds. A Mean Normal I-STAT prothrombin time (sec) and an ISI are determined following the WHO recommendations at a CAP accredited facility. The reported INR time is derived from the P T result in an equation using an ISI of 1.05 and a typical Mean Normal Plasma PT time of 12.0 seconds.

INR= [ Patient I-STAT Prothrombin time ] ISE

[Mean Normal I-STAT Prothrombin time]

10.0 UNACCEPTABLE RESULTS

The followings are conditions in which results are unacceptable and a venous draw should be ordered for assay by the Clinical Laboratory:

  • When patient result displays INR0.8 or 4.5.
  • When patient result INR is drastically different from last fingerstick INR result.
  • When patient results are obtained from a meter that has failed QC or error codes occur during patient testing. In this case, the patient may be retested by a second fingerstick or a venous draw can be ordered for assay by the Clinical Laboratory.

11.0 REPORTING RESULTS

  1. Patients’ results are reported in INR units and PT seconds with the fingerstick and venous draw.
  1. Quality Controls results and assay ranges are reported as INR They are logged in the I-STAT PT QC and Patient log.
  1. Oral Anticoagulation Clinic (OAC) only reports results obtained using the I-STAT meters at the clinic, or results from venous draws from Clinical Laboratory. The OAC will is not responsible for results obtained from patients’ own meters or other laboratories since no correlation and validations are conducted with outside testing devices. Physicians are cautioned to consider differences in test methodology and reference ranges when interpreting INR and PT values when comparing laboratory results from different sources with those obtained at OAC.
  1. Notify the Licensed Independent Practitioner (such as the physician or Nurse Practitioner, etc) responsible for the test results as outlined in the Critical Test.

12.0PROCEDURAL NOTES

  1. Poor technique in sample collection may compromise the results.
  2. The I-Stat PT/INR test is insensitive to fibrinogen concentration between 70 and 541 mg/dL.
  3. The I-STAT PT/INR test is insensitive to heparin up to 1.0 U/mL.
  4. Hematocrits in the range of 24-54% PCV have been demonstrated not to affect results.
  5. PT/INR may be affected by commonly administered drugs.
  6. Glass syringes or tubes may prematurely activate coagulation, resulting in accelerated clotting times and lower INRs.
  7. The presence of exogenously added heparin, citrate, oxalate, or EDTA from blood collection devices will interfere with test results.

13.0 REFERENCE / THERAPUETICRANGES

  1. ReferenceNormalRanges for INR is 0.9- 1.1 (same as in-lab instrument)
  2. Therapeutic Ranges:

If patient is on Warfarin, therapeutic range is 2.0 – 4.5 INR.

(Low Intensity therapeutic range is 2.0 – 3.0 INR).

(High Intensity therapeutic range is 3.0 – 4.5 INR).

14.0 PANIC VALUES

When patient’s INR > 4.5, the pharmacist or attending physician shall be contacted to determine whether to order a venous draw to be assayed in the Clinical Laboratory which has the capability to report the INR and PT result in the range above INR 4.5. The Clinical Laboratories will call test site personnel when patient INR >4.5 or <1.5. The attending physician or pharmacist will assess patient risk for bleeding. If risk is low, he or she will manage the patient’s dosage per protocol. By State regulations, pharmacists are licensed to adjust Warfarin dosages. The Medical Director will be notified if patient is bleeding or clinically unstable.

15.0 LIMITATIONS

  1. Do not use damaged or expired test cartridges or controls.
  2. Many drugs influence coagulation and affect prothrombin time results. Clinical decisions based on prothrombin time measurements must be made with a careful assessment of effect those different drugs and disease states have on coagulation. An unanticipated abnormal prothrombin time result should always be followed up with appropriate coagulation studies to define the cause of the abnormal result.
  3. For AnalyticalRange: I-STAT does not report Whole Blood PT results <0.9INR or >8 INR.
  4. INR values less than 0.9, are displayed as “INR0.9”.
  5. INR values greater than 8.0 are displayed as “INR>8.0”.

F.Should I-STAT instrument fails to work properly, after obtaining an order, citrated samples should be drawn and sent to Clinical Laboratories for INR/PT analysis.

16.0 CLINICAL INTERPRETATION

Prothrombin time has been shown to be sensitive to deficiencies of factors II, V, VII, IX and X. The test can be useful in monitoring the prolonged coagulation response of patients undergoing coumadin therapy. Many diseases and drugs can prolong or prevent coagulation by altering the balance of clotting factors involved in coagulation. Rare inhibitors affecting the PT have been described, which may require screening with a PT mixing study in the clinical laboratory. Each physician should establish expected INR / PT values for his/her patients.

17.0 MAINTENANCE

A.Routine Maintenance

  1. Dock meters daily

2.Run monthly Liquid QC on Level 1 and Level 2

3.Visual inspection of meters to be sure no blood or fluids are spilled on the meters. If meters are soiled, wipe with a paper towel moistened with 10% bleach solution and then dry with a clean towel thoroughly.

4.Daily checking and recording of cartridge lot# and expiration date in use.

B.Service

A. Call Point of Care Testing Department at 724-8934 for assistance

C.Battery Care

A.Order 9 volt batteries from Central Supply and keep on hand.

B.The batteries should be changed immediately when the flashing battery appears on the screen.

18.0 TROUBLESHOOTING

IF … / THEN …
The repeat result is still outside the expected range. / Send the patient to have a sample drawn and sent to Clinical Lab to check.
Liquid QC not within ranges / Check Cartridge and control expiration dates. Use a new vial of control and repeat testing. Call POCT if still out.
Patient results appear to be inaccurate. / Check conditions which may affect test accuracy:
  • Air bubbles in the sample
  • Hemolysis
  • Clotted or partially clotted blood
  • Unsuspected anticoagulation with either heparin or warfarin.
  • Presence of a circulating anticoagulant / inhibitor.

19.0 TESTING PERSONNEL

Licensed healthcare providers including, Registered Nurses, Pharmacists, and Pharmacist Residents who have been trained by the Point-Of-Care-Testing department are authorized to use the I-STAT instrument. Initial training, 6-month and annual competencies are required to maintain competency and testing privileges. Retraining is required if competency is not maintained at stated intervals. Each authorized user is required to use his/her operator ID when QC and patient testing are performed. Use of another person's ID or inappropriate use of a "dummy" ID may be grounds for revoking POCT testing privileges and / or a cause for disciplinary action. Pharmacy Technicians and Pharmacist students are allowed to perform QC testing only and no patient testing is allowed.