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Chapter 1 General of Clinical Laboratory LI Ping General of clinical laboratory Principles to clinical laboratory The interpretation of laboratory tests The ethical practice Principle to clinical laboratory Responsibilities Collection of Information Collection of Specimens (Informed consent 、 Adequate privacy) Performance of Test Reporting of Result Storage and Retention of Medical Records Access to Medical Records Responsibilities The patient----assurance the quality and integrality of the service Colleague and professional -----maintain professional reputation, aim to contribute the advancement of profession Society----contribute to the general well-being of society ; comply with relevant laws and regulations of professional activities. Collection of information Identify adequately patients and specimens Enable the test to be correctly interpreted Other legitimate purposes Performance of the test Accreditation Patients program interests Works with high skill Process and competence standard Good performance of tests Reporting of Result Test results are confidential unless disclosure is authorized. Report the results correctly and timely Provide the consultation about the selection and interpretation of tests properly Access to Medical Records Who?? • clinician requesting the test; • the patient; • laboratory and hospital staff if required for the management of the patient; • other authorized individuals. When a request is made for access to test results by an authorized person, the laboratory must first satisfy itself as to the identity of the person making the request. INTERPRET LABORATORY TEST suboptimum selection Biological Testing Cycle variability ,improper Select test or inconsistent preparation Make clinical Patients prepare decision Minimize variability for sampling No confusion and Improper or inconsistant Check 、report misunderstanding Collection result about test results Collect specimen Inadequate Improper RVs provision Pre-process of Analyze specimen Analytical specimen variabilty Biologic variatinon Endogenous biorhythms Different constitutional factors for physiologic parameters and lifestyle among subjects within-subject variation subject-to –subject variation Biological variation Biological rhythms Constitutional Width of the test’s factors Referenc interval (RI) Extrinsic factors the diagnostic efficiency of a laboratory test Three types of Biological rhythms Circadian Ultradian Infradian Rhythms Rhythms Rhythms Cycle time 24h <24h >24h Character Consistent Inconsistent unknow Predictable Unpredictable solution rhythm- stimulation and unknow adjusted RVs suppression tests example Number and gonadal menstrual activity of hormone cycle blood cell Biologic variation endogenous biorhythms Different constitutional factors for physiologic parameters and lifestyle among subjects within-subject variation subject-to –subject variation Biological variation Biological rhythms Constitutional Width of the test’s factors Referenc interval (RI) Extrinsic factors the diagnostic efficiency of a laboratory test Biologic variabilty —— Constitutional factor Age rapid physiologic changes infants 、hemolysis 、 bilirubin children Plasma protein enzyme Age sex hormones specific age reference adults constant until menopause in limits women and middle age in men elderly age-related differences in nutrition 、intercurrent disease Biologic variabilty – Constitutional factor Genetic heterogeneity Genetic phenotypic differences heterogeneity Different reactivity Different concentration towards nucleic acid of analyte probes and antibodies false-negative Misleading Biologic variabilty - Extrinsic Factors Posture homeostasis of rennin vascular tone aldosterone catecholamines supine stand plasma volume H 2O Small analyte Concentration of nondiffusibl analyte vascular interstitial space Biologic variabilty – Extrinsic Factors Exercise • shifts in plasma water • glomerular filtration rate • urine production • release of macromolecules from cells and tissues Biologic variabilty - Extrinsic Factors Diet meal related fasting related TG TC Lac BUN Acetone GLU Glucagons …….. ………. Recommendation : duration of fasting before specimen collection is typically 12 hours Biologic variabilty – Extrinsic Factors Drug Types of Interference —— Analytical interference Physiologic interference Recommendation —— Recognize drugs’ potential for occurrence, withdraw medications before sampling whenever possible, Evaluat any suspicious results in light of a subject’s medication history. Biologic variabilty- Extrinsic Factors Pregnancy plasma volume hyperventilation erythrocyte mass altered distribution of cardiac output plasma protein endocrinologic synthesis changes Biologic variation-summary Biological rhythms—— Circadian , Ultradian ,Infradian rhythms Constitutinal factors—— Gender, age, gene Extrinsic factors—— Posture, Exercise, Diet, Drugs, Pregnancy , Caffeine, Alcohol use, Oral Contraceptives, Intercurrent Illness Establish and validate RVs Establish clinical performance characteristics Help clinician to select the most effective tests and testing strategies Why? Help clinician to translate laboratory results into a probability statement Help the laboratory director to focus the resources of the laboratory on tests with the highest clinical relevance phase II and phase III How ? Collect data clinical trials Establish and validate RVs ??? How to assure the validity of the parameters derived from clinical trials? Use gold standard to define every subject’s status A broad spectrum of healthy and diseased subjects, include patients with a wide range of clinical presentations. CIs should be calculated for all the parameters that are estimated. When new test compares with the old test, assure sample of patients large enough and data exactly . Sensitivity and Specificity Disease Test result Total status Positive negative Disease TP FN TP +FN Healthy FP TN FP +TN Total TP +FP FN+TN TP+FP +TN+FN Sensitivity and Specificity Sensitivity(Se)=TP/ (TP+FN) Express the probability that a diseased subject will have an abnormal result Specificity(Sp)=TN/(TN+FP) Express the probability that a nondiseased patient will have a result within the RI Predictive Value PV+ =TP /(TP+FP ) The probability that a subject with a positive test result truly has the disease PV- =TN/(TN+FN ) The probability that a subject with a negative test result truly is healthy . Note PVs are only accurate when the test is applied to populations with a disease prevalence that is similar to that of the study sample. ROC Curves ?? What is ROC curve used for ? Determine the most efficient decision threshold or cutoff value for a laboratory test. Compare the relative clinical accuracies of different laboratory tests in a particular clinical setting ROC Curves Likelihood Ratios LHR express the probability that a particular will occur in a diseased subject divided by the probability that the same outcome will occur in a nondiseased subject. LHR+ =Se/(1-Sp) LHR-=(1-Se)/Sp =TP rate/FP rate =FN rate/TN rate For continous variable test,LHRs can be established for different ranges of test results, so the magnitude of a test result provides additional discriminatory power Likelihood Ratios LHR+ =TP rate/FP rate TP rate represent benefit of the test ,FP rate represents the costs associated with testing ,so LHR+ represents a cost-benefit ratio .It is similar to LHR-. The LHR+ and LHR- allow the direct estimation of the posttest probability of disease in view of the new information contributed by the test result . Likelihood Ratios LHR allow the information from different modalities to be combined in serial diagnostic schemes or “critical pathways” for which overall predictive values can be calculated. Estimating LHR from ROC Curves LHRs for a particular test can also be obtained directly form a ROC curve by evaluating the slopes of the curve in different regions continuous variable test positive /negative test test that classified into more than two intervals ETHICAL PRACTICE Definitions Ethical practice can be regarded as appropriate technical practice accompanied by integrity in attitudes and behavior. Why Do We Need Ethics? Medical laboratory services are an integral part of medical services, The same standards and ethical principles that govern the delivery of clinical services will also apply to the delivery of laboratory services. ETHICAL PRACTICE Doctor-Patient Relationship Technically competent service Consultation (select and interpret the tests) Protect the patients’ interests Common Requirements Of Medical Laboratory Ethics Confidentiality Medical ethics exist for the protection of patients, and this protection must not be compromised. Special Requirements Of Medical Laboratory Ethics Principles Of Ethics Medical Ethics Autonomy、Beneficence、Nonmaleficence 、Justice Ethics In Medical Laboratories The ethical standards of those working in medical laboratories are derived from medical ethics and incorporate the same principles.
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