lab values interpretation resources update 2013
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Acute Care Section-APTA The Critical Edge www.acutept.org
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It is the professional responsibility of the physical therapist to interpret available laboratory values as a component of the examination and evaluation of a patient/client, to suggest laboratory testing when indicated, and to use lab values to guide the determination of safe and effective interventions for the patient/client. We, as physical therapists, act as consultants in the rendering of our professional opinion and bear the responsibility to advise the referring practitioner about the indications for physical therapy intervention. The Acute Care Section-APTA created this referenced resource for members to provide updated information and guide your inquiry into lab value interpretation. In this document you will find the following:
Acute versus Chronic & Risk versus Benefit Considerations Sex and Gender Considerations Race and Culture Considerations Tips for Collegial Discussions with Healthcare Providers Peer Reviewed Resources Websites Search Engines Updated Lab Values and Relevant Resources Pulmonary Function Tests Anticoagulation for Venous Thromboembolism Recommended Reading List Selected full-text articles
o Polich S. Competency based assessment in acute care: theory behind the practice. Acute Care Perspectives. 2006;15(1):1-6.
o Garritan S, Jones P, Kornberg T, Parkin C. Laboratory values in the intensive care unit. Acute Care Perspectives. 1995;3(4):7-11.
o Costello E, Elrod C, Tepper S. Clinical decision making in the acute care environment: a survey of practicing clinicians. J Acute Care Phys Ther. 2011;2(2):46-54.
DISCLAIMER: The Acute Care Section-APTA has provided this information as a resource to the membership. The Section will not interpret lab values as this is the professional responsibility of every clinician.
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ACUTE VERSUS CHRONIC CONSIDERATIONS In addition to reviewing the patients lab value and the given reference range, the therapist should also consider the chronicity of the change in the lab value. Acute changes, such as those associated with blood loss due to trauma or surgery, may require the therapist to select a more conservative plan of care. Acute changes in lab values may have more severe adverse events in patients due to the limited amount of time for the patients system to compensate for this acute change. More chronic changes in lab values, commonly associated with chronic conditions (e.g., CHF, COPD) or longer term medical interventions (e.g., chemotherapy, radiation therapy) allow the patient a period of time for their body to adapt or attempt to adapt to the changes in lab values, which may allow them to have more resources to deal with potential adverse events caused by increasing cardiorespiratory demand, mobility, and exercise. RISK VERSUS BENEFIT CONSIDERATIONS The fundamental consideration when evaluating lab values to determine appropriate physical therapy plan of care revolves around the risk to the patient posed by proceeding with intervention versus the benefits gained by the intervention. The therapist should carefully consider all the potential adverse events that may present during intervention based on the lab values out of the reference range, and consider the elevated risk should a value fall in the critical range. Understanding of the lab test in question and the potential adverse events is critical to this aspect of patient care. Likewise, the therapist should consider the potential benefits of increased mobility and exercise that proceeding with the intervention may provide to the patient. Not only should the immediate risks and benefits of the therapy session in question be considered, but also the longer term risks and benefits over the episode of care that may be present. Often it may be that the therapist will need to consult with other members of the medical team to fully explore the risk versus benefits of physical therapy intervention, and assist with the development of facility policies, procedures, and/or protocols to assist in clinical decision making regarding the use of lab values in determining aggressiveness of physical therapy intervention.
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SEX AND GENDER CONSIDERATIONS Many lab results will have reference ranges reported as age-specific or sex-specific values. With regards to interpretation of these reference ranges regarding sex-specific norms, the therapist needs to consider the patients biological sex, gender, and gender identity to avoid referencing the incorrect normal value. A review of the differences of these terms is provided in Table 1. Table 1. Definitions pertaining to sex and gender roles.1
Term Definition Sex Categorical differentiation between men and
women, assigned at birth based on brief visual examination of external genitalia
Gender Binary social construct involving characteristics distinguishing men from women
Persons sense of being male or female
Transsexual Outdated term for person who feels they were assigned the incorrect sex
Transgender Overarching term for persons with various identities and expressions that are associated with assignment of incorrect sex
Transition Legal, medical, and surgical processes that a transsexual person may go through to correct the incongruence of incorrect sexual assignment
Transwoman A person who identifies as female but was assigned the male sex
Transman A person who identifies as male but was assigned the female sex
Individual patients may be in the process of transitioning to their preferred gender through medical (i.e., hormone replacement therapy), surgical (i.e., gender reassignment surgery), and/or legal (i.e., amending legal documents to reflect gender identity) means to correct incongruence of sex. Therapists should determine if patients in transition are currently under treatment for medical transition, which may occur prior to or in conjunction with surgical transition, and will be continued after surgical transition. If the patient is on hormone replacement therapy, you should use the transitioned gender to determine the reference value. If the patient is not receiving hormone therapy, you should use their biological sex to determine the reference value. For example, a transwomen on estrogen replacement therapy should have their lab values compared to normal values of females due to the effects of estrogen on their physiology, whereas a transman on testosterone should have their lab values compared to those of males due to the effects of testosterone on their physiology. The key factor is not whether the medical record assigns the patient a particular sex nor if the patient has undergone sexual reassignment surgery, but whether they are taking hormone therapy that will affect their
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physiology and lab chemistry. Knowing the medical transition status of a transsexual person can result in avoidance of misinterpretation of lab values and ensure correct application of normal reference values consistently. Reference
1. Polly R, Nicole J. Understanding the transsexual patient: culturally sensitive care in emergency nursing practice. Adv Emergency Nurs J. 2011;33(1):55-64.
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RACE AND CULTURE CONSIDERATIONS Census 2010 indicated increased minority demographic shifts in the United States.1 McClatchey noted that genetic heterogeneity within a population leads to person-to-person phenotypic differences that can contribute to the variability in laboratory test results.2(p101) In addition, due to culture and food preferences, it is not possible to determine whether racial differences in laboratory values are genetic or related to lifestyle alone (e.g., cholesterol).3 Therefore, physical therapists should be mindful of racial differences in laboratory values and recognize that racial differences are not easily conclusive because it is often difficult to separate effects of race per se from those of other factors. Genetic heterogeneity at the molecular level can lead to differences in the reactivity of a patients DNA, proteins, or cells toward the nucleic acid probes and antibodies that are used as reagents in many diagnostic tests.2 This type of genetic heterogeneity can result in false-negative findings. Genetic variability will become an increasing consideration for development of tests and analyzing test results as the field of clinical laboratory medicine progresses. In the United States, African Americans tend to have increased muscle mass and skeletal structures than their Caucasian counterparts. Therefore, racial differences in serum levels of creatine kinase and lactate dehydrogenase in adults and in serum alkaline phosphatase in children are noted. African Americans also tend to have higher serum total protein levels and higher serum levels of alpha, beta, and gamma globulins, IgG, and IgA than Caucasians.2 There is a difference in hemoglobin (Hgb) values with African Americans having lower hemoglobin compared to Caucasians.3 In addition, HgbA1c (A1C) lab values can be altered in patients with sickle hemoglobin, which is present in 8% of the African American population.4 Other studies have noted white-black differences in