Contrast To Detection Of Three Coagulation Markers By Two Testing Systems

Background:Increasing number of patients has suffered from hemorrhagic disease and thrombotic disease clinically. Prothrombin Time (PT)-INR, Activated Partial Thromboplastin Time (APTT) and Fibrinogen Coagulative Time (FIB), are the three basic items in diagnosing hemorrhagic and thrombotic disease as well as the necessary items for coagulation system testing, requiring the laboratory to provide proper data.PT and APTT are used in screening test for exogenous and endogenous coagulation system and are especially of clinical significance for the test of blood diseases, DIC, cerebral hemorrhage, liver disease, acute and chronic infection, cerebral infarction and myocardial infarction. PT and APTT are the two major testing items for surgical screening as well as the preferred indicators in monitoring oral anticoagulant therapy.With rapid upgrading of testing equipments, coagulation analyzer is commonly used in large, medium and small hospitals. Each laboratory at least owns large and small-sized coagulation analyzers respectively, which requires accuracy and consistency of the testing results. However, laboratory examination of coagulation system is based on multivariate analysis. There is no linear relationship between the various indicators and the concentration of the coagulation factors. Different testing methods, reagents and testing instruments may lead to different testing results, making it difficult for comparison between inter-laboratory and inner-laboratory testing results.Objective:There are two coagulometers available at present, one is START-4 Channel Semi-automatic blood coagulometer produced by STAGO company that adopts solidification (magnetism bead) method in testing; the other is CA7000 automatic blood coagulometer produced by SYSMEX Company that adopts optical testing (light-scattering turbidimetry method). Contrast evaluation on both coagulometers of different testing systems (different models, different detection principles and different reagents) is made to study whether both testing systems are different in detecting PT, (INR), APTT and FIB, whether the difference makes a sense in statistics and how to make it conducive for clinical interpretation. Such evaluation is of great significance for routine coagulation test in hospitals and provides reference data for other laboratories using the same kinds of instruments.By contrast, we have effectively improve the comparability of different blood coagulometers, can immediately detect the accidental errors and systemic error of the instrument and help staffs to solve various kinds of existing problems. Meanwhile, we try best to minimize unnecessary medical disputes arising from varying results given by instruments of different models and effectively guarantee accuracy and precision of the testing results and improve the quality of the test.Methods:1. Instrument precision testing:refer to National committee for clinical Laboratory Standards (NCCLS), first make a rough determination of the within-run precision by selecting a portion of mixed plasma from 40 normal subjects, detecting continuously for 20 times on both instruments separately and calculating the SD and CV of PT, APTT and FIB to evaluate the within-run precision; Then divide the mixed plasma from normal subjects into 20 portions in 20 tubes and detect twice a day for 20 days on ends to calculate the SD and CV of PT, APTT and FIB and evaluate the between-run precision, thus to reflect the repetition of the both instruments.2. Instrument accuracy testing:test DADE medium-valued and high-valued quality control materials on CA7000 separately for continuously 20 times and calculate the mean value, standard deviation, coefficient of variation and coefficient of deviation. Likewise, test STAGO medium-valued and high-valued quality control materials on START-4 separately for continuously 20 times to verify the accuracy of both detection systems.3. Comparison test:select conventional coagulation samples of different clinical scopes (normal value and abnormal value) and test the samples simultaneously on both instruments every day; record 20 sets of medium-valued PT, APTT and FIB results and 20 sets of high-valued results. Suppose CA-7000 is the reference instrument and the values detected from it are the target values and START-4 is the testing instruments and the values detected from it are testing values, then make correlation comparison and calculate the relevant coefficient r and slope value a. Use paired t-test to calculate value t and value p of each group.4. Anti-interference test:prepare specimen for test by in vitro addition of interferents to normal plasma according to the National committee for clinical Laboratory Standards (NCCLS) guideline and carry out paired t-test; collect blended fresh plasma and divide the samples into two portions, one is added with suspected interferent as the testing specimen (T); the other is added with distilled water of the same volume as the control specimen (C). Test the both specimens on the two instruments simultaneously. If the disturbed value on control group falls within the±1.96SD (95% confidence limit) scope, there is no distinct interference; if the disturbed value exceeds the scope, it shows there is interference to the test of clinical specimen. Result:1. After within-run test, both detection systems determined CV value of <5% for PT(INR), APTT and <6.6% for FIB respectively. All the coefficients of variation are within permitted range with good repetition. CA7000 tested the between-run CV for PT,INR,APTT and FIB of 2.2%,1.9%,2.9% and 4.4% respectively; START-4 tested the between-run CV for PT,INR,APTT,FIB of 3.8%,2.5%,4.3% and 5.9% respectively. START-4 tested the between-run CV of 4.0%,3.4%,4.6% and 6.8% separately. The CV value tested by automatic coagulometer CA7000 is less than the CV value tested by semi-automatic coagulometer. The within-run CV value is less than between-run CV.2. When using CA-7000 instrument and auxiliary reagents to detect the accuracy of DAEA medium-valued and high-valued quality control materials, the CV values are <5% and 6.6%, with deviation coefficient of <5% and coincidence rate of 95%; when using START-4 instrument and auxiliary reagents to detect the accuracy of the STAGO medium-valued and high-valued quality control materials, the CV values are <5% for all but FIB with deviation coefficient of <5%.3. By comparison on testing results on patient samples within range of normal value and abnormal value of CA7000 and START-4 system, there is significant statistical difference for the testing result of p<0.05 for the both systems. The correlation comparison between the CA 7000 system and START-4 system as reference method showed a good correlation between the both methods with R value of >0.9.4. Interference test on both instruments shows START-4 has strong anti-interference ability with testing results for hyperlipemia,hemolysis and hyperbilirubinemia of within±1.96SD range, indicating of no interference. CA7000 is relatively poor in anti-interference. When concentration of free hemoglobin in specimen hemolysis reached 20g/L, the CA7000 testing result of PT and APTT are distinctly prolonged, FIB is reduced and the disturbed value of all the three indexes exceed the range of±1.96SD, indicating that the three indexes are simultaneously disturbed. When triglyceride concentration reached 21.6mmol/L,36mmol/L, 43.2mmol/L by CA7000 testing, the testing results of FIB, PT, APTT are disturbed in turn, the testing result exceeds 120s, the disturbed value is also beyond the range of±1.96SD.FIB and APTT are tested to be the worst and best in anti-interference capability respectively. Neither instrument is disturbed when total bilirubin is within 353μmol/L, indicating the instruments have a strong anticteric capability.Conclusion:With widely popularization of the thrombosis and hemostasis testing at present, the performance of coagulometer is becoming more stable. The two testing systems of the both caogulometers in our laboratory have good repetition and accuracy and meet the clinical requirements for testing precision and accuracy. The precision of the automatic coagulometer is better than that of the semi-automatic coagulometer. Semi-automatic coagulometer is relatively complicate in operation and is vulnerable to the impact of the operator's proficiency and thus may give wrong result or no result and may often require retesting. The automatic coagulometer is free from impact of subjective factors and may test several indexes at one time with fast speed.Through contrast testing, we can see that the two different testing systems have produced different results. Statistical analysis shows that the two systems have produced distinctly different testing results for PT (INR), FIB and APTT. This may due to different sensitivity of the auxiliary reagents produced by two companies. In addition, different methodologies may also result in different testing results.We conclude that the results on Routine Blood Coagulation produced by the two different testing systems vary greatly, thus it's better to use the same testing system in one laboratory. If there are different testing systems in one laboratory, blend plasma from normal human should be subjected to contrast testing on regular basis as well as the interlaboratory quality control every day as that has been done to patient samples. As the both systems produce significantly different testing results on PT (INR), FIB, APTT, we should establish different reference ranges for the two different testing system. Each testing system should make clinical interpretation within its own reference range.With respect to the two coagulometers in our laboratory, Sysmex CA7000 is an automatic one that features convenient operation, excellent repetition and fast speed and can be used for routine works. However, STAGO-START 4 channel semi-automatic coagulometer is more effective in performance of anti-interference of lipemia, hemolysis and jaundice. Therefore, both coagulometers may complement each other and produce testing results within their own reference range.