Management Lung abscess Posturaldrainage purchase generic zoloft canada mood disorder inventory,physiotherapyandaprolongedcourse of appropriate antibiotics to cover both aerobic and Deﬁnition anaerobic organisms will resolve most smaller ab- Localisedinfectionanddestructionoflungtissueleading scesses order 50mg zoloft amex mood disorder rage. Largerabscessesmayrequirerepeatedaspiration buy 100mg zoloft definition von depression, to acollection of pus within the lung. Organismswhichcausecav- Deﬁnition itation and hence lung abscess include Staphylococcus Thereareessentiallythreepatternsof lungdiseasecaused and Klebsiella. Pathophysiology Aetiology The abscess may form during the course of an acute It is a ﬁlamentous fungus, the spores (5 µmindiame- pneumonia, or chronically in partially treated pneu- ter) are ubiquitously present in the atmosphere. The pattern of disease that arises depends 108 Chapter 3: Respiratory system on the degree of tissue invasiveness, the dose inhaled and Aspergilloma the level of the host’s defence. This results from Aspergillus growing within an area of previously damaged lung such as an old tuberculous Allergic bronchopulmonary aspergillosis cavity (sometimes called a mycetoma). Seen on X-ray as a round lesion with an air ‘halo’ above i Initially it causes bronchospasm which commonly it. In immunosuppressed individuals with a low granulo- iii Chronic infection and inﬂammation leads to irre- cyte count, the organism may proliferate causing a severe versible dilatation of the bronchi (classically proximal pneumonia, causing necrosis and infarction of the lung. The organisms are present as masses of hyphae invad- iv If left untreated progressive pulmonary ﬁbrosis may ing lung tissue and often involving vessel walls. Investigation Theperipheralbloodeosinophilcountisraised,andspu- Management tum may show eosinophilia and mycelia. Eosinophilic Invasive aspergillosis is treated with intravenous am- pneumonia causes transient lung shadows on chest X- photericin B (often requiring liposomal preparations ray. Itraconazole and voriconazole have been used more re- Lung function testing conﬁrms reversible obstruction in cently but current studies comparing efﬁcacy with am- all cases, and may show reduced lung volumes in cases photericin B have yet to prove deﬁnitive. Management Obstructive lung disorders Generally it is not possible to eradicate the fungus. Itra- conazole has been shown to modify the immunologic Asthma activation and improves clinical outcome, at least over the period of 16 weeks. Oral corticosteroids are used to Deﬁnition suppress inﬂammation until clinically and radiograph- A disease with airways obstruction (which is reversible ically returned to normal. Maintenance steroid therapy spontaneously or with treatment), airway inﬂammation may be required subsequently. The asthmatic compo- and increased airway responsiveness to a number of nent is treated as per asthma guidelines. Chapter 3: Obstructive lung disorders 109 Incidence Pathophysiology 20% of children, 5–14% of adults, increasing in preva- The clinical picture of asthma results from mixed acute lence. With time this repeated stimula- Can present at any age, predominantly in children. They secrete mediators of acute and 2 Intrinsic asthma tends to present later in life. There is chronic inﬂammation including enzymes and oxygen no identiﬁable allergic precipitant. Patients with occupational asthma from the listed causes are entitled to compensation under in- inﬂammation recruiting and activating ﬁbroblasts dustrial injuries legislation in the United Kingdom. They also lead, through r Forall patients, non-speciﬁc irritant trigger fac- mechanisms which are not yet clearly deﬁned, to tors include viral infections, cold air, exercise, bronchialhyperresponsiveness–anexaggeratedbron- emotion, atmospheric pollution, dust, vapours, choconstrictor response to non-speciﬁc insults to the fumes and drugs particularly nonsteroidal anti- airways. The pattern of airway reaction following inhalation of an allergen: i An acute reaction occurring within minutes, peaking Table3. Non IgE related Isocyanates, colophony fumes (from ii A late reaction occurring 4–8 hours after inhalation solder), hardwood dust, complex (the chronic inﬂammatory response). If there is diagnostic difﬁculty in patients with mild symp- Mild–moderate Life-threatening attack Severe attack attack toms or just cough, exercise tests or peak ﬂow diary card r r r recordings as above. Occasionally, a trial of oral corti- Speech normal Unable to Silent chest costeroids for 2 weeks can be used. Skin tests are used complete sentences to identify speciﬁc allergens and serum can be taken for r Pulse <110 r Pulse ≥110 r Cyanosis total and speciﬁc IgEs. An asthma attack is characterised by rapid inspiration, r Allergen avoidance can be advised, e. However these rarely have a major im- tial severity of asthma patients require rapid assessment pact on disease. An acute asthma attack is classiﬁed r Drug therapy includes: short acting β agonists for 2 according to clinical severity (see Table 3. Night-time waking, early phyllines and other agents with additional activities morning wheeze, acute exacerbations in the preceding (see Fig. Once disease control is achieved the steroid dose is reduced under regular review to Complication the minimum dose required to maintain disease Pneumothorax, surgical emphysema due to rupture of control. How- should not be reduced more frequently than every 3 ever, the test may be falsely negative if the asthma is months. Chapter 3: Obstructive lung disorders 111 Step 5: Continuous or frequent oral steroids Daily oral steroids in lowest dose providing adequate control whilst continuing maximal inhaled steroids and use of other steroid sparing agents. Refer patient for specialist care Step 4: Persistent poor control Consider trial of: • Very high dose inhaled steroid • Addition of a fourth drug e. Prognosis Most children and teenagers with asthma improve as Prevalence they get older, although asthma may recur in adult life. Em- All patients should be advised not to smoke and to avoid physematous spaces are found in 50% of smokers aged potential work allergens. Chronic bronchitis and emphysema Sex Deﬁnition M > F Chronicbronchitishasaclinicaldeﬁnitionofcoughpro- ductive of sputum on most days for at least 3 months of Geography the year for more than 1 year. New regression equations for predicting Patients with severe asthma (indicated by need for admission) and adverse peak expiratory flow in adults. Expiratory wheeze and cough are present Virtually conﬁned to cigarette smokers and related to the but the cough is dry. As emphysema be- causes pan-acinar emphysema and accounts for 5% of comesmoresevereothersignsbecomeevidentinclud- patients with emphysema. One in 5000 births have a ho- ing tachypnoea, cachexia, the use of accessory muscles mozygousdeﬁciencyandmostthesegoontodevelopthe of respiration, intercostal recession, pursed lips on ex- lung disease. Patients tend to be young (below 40 years) piration, poor chest expansion (a hyperinﬂated chest especiallyifsmokers,inwhomthediseaseismuchworse. The pink puffer is typical of relatively of airways and luminal narrowing resulting in airway pure emphysema and the blue bloater is typical of rel- obstruction. Mucus respiratory bronchioles whilst the more distal alveolar gland hypertrophy and hyperplasia can be quantiﬁed by ducts and air spaces tend to be well preserved. The theReidindexwhichistheratioofglandtowallthickness alveolar dilatation results from loss of elastic recoil in within the bronchus. Smoking Microscopy also causes glandular hypertrophy (chronic bronchi- Both emphysema and chronic bronchitis are inﬂam- tis) and has an adverse effect on surfactant favouring matory diseases of the lung. In pan-acinar emphysema destruction involves the Eosinophilsarealsoseenespeciallyinchronicbronchitis, whole of the acinus. Theclinicalfeaturesdepend Complications on the degrees of chronic bronchitis and of emphysema Airway obstruction and alveolar destruction eventually contributing to the overall picture. Pulmonary vasculature re- ductive of sputum, expiratory wheeze and progres- sponds to hypoxia by vasoconstriction which increases sive shortness of breath. Symptoms of emphysema the arterial pressure, causing pulmonary artery hyper- are dominated by progressive breathlessness, initially tension, which leads to right heart failure (cor pul- only on exertion but eventually on mild exertion such monale).
Basic and advanced procedural skills: Students should be able to: • Insert a nasogastric tube proven 50mg zoloft endogenous depression definition psychology. Management skills: Students should be able to develop an appropriate evaluation and treatment plan for patients that includes: • Recognizing the role of narcotic analgesics and empiric antibiotics in treating selected patients who present with acute abdominal pain cheap zoloft 50mg line bipolar depression not typical otherwise specified. Demonstrate commitment to using risk-benefit buy zoloft 50 mg line depression kills, cost-benefit, and evidence- based considerations in the selection of diagnostic and therapeutic interventions for abdominal pain. Recognize the importance of patient needs and preferences when selecting among diagnostic and therapeutic options for abdominal pain. Recognize the importance and demonstrate a commitment to the utilization of other healthcare professions in the treatment of abdominal pain. Internists must master an approach to the problem as they are often the first physicians to see such patients. The pathophysiology, symptoms, and signs of the most common and most serious causes of altered mental status, including: • Metabolic causes (e. The importance of thoroughly reviewing prescription medications over-the- counter drugs, and supplements and inquiring about substance abuse. The risk and benefits of using low-dose high potency antipsychotics for delirium associated agitation and aggression. History-taking skills: Students should be able to obtain, document, and present an age-appropriate medical history that differentiates among etiologies of altered mental status including eliciting appropriate information from patients and their families regarding the onset, progression, associated symptoms, and level of physical and mental disability. Physical exam skills: Students should be able to perform a physical exam to establish the diagnosis and severity of disease, including: • Complete neurologic examination. Differential diagnosis: Students should be able to generate a prioritized differential diagnosis recognizing specific history and physical exam findings that suggest a specific etiology for altered mental status. Laboratory interpretation: Students should be able to recommend when to order diagnostic and laboratory tests and be able to interpret them, both prior to and after initiating treatment based on the differential diagnosis, including consideration of test cost and performance characteristics as well as patient preferences. Communication skills: Students should be able to: • Communicate the diagnosis, treatment plan, and subsequent follow-up to the patient and his or her family. Management skills: Students should able to develop an appropriate evaluation and treatment plan for patients that includes: • Recognizing that altered mental status in a older inpatient is a medical emergency and requires that the patient be evaluated immediately. Appreciate the family’s concern and at times despair arising from a loved one’s development of altered mental status. Appreciate the patient’s distress and emotional response to that may accompany circumstances of altered mental status. Demonstrate commitment to using risk-benefit, cost-benefit, and evidence- based considerations in the selection diagnostic and therapeutic interventions for altered mental status. Recognize the importance of patient preferences when selecting among diagnostic and therapeutic options for altered mental status. Demonstrate ongoing commitment to self-directed learning regarding altered mental status. Appreciate the impact altered mental status has on a patient’s quality of life, well-being, ability to work, and the family. Recognize the importance of and demonstrate a commitment to the utilization of other healthcare professionals in the diagnosis and treatment of altered mental status. Distinguishing among the many disorders that cause anemia, not all of which require treatment, is an important training problem for third year medical students. Morphological characteristics, pathophysiology, and relative prevalence of each of the causes of anemia. The classification of anemia into hypoproliferative and hyperproliferative categories and the utility of the reticulocyte count/index. The potential usefulness of the white blood cell count and red blood cell count when attempting to determine the cause of anemia. History-taking skills: Students should be able to obtain, document, and present an age-appropriate medical history, that differentiates among etiologies of disease, including: • Constitutional and systemic symptoms (e. Physical exam skills: Students should be able to perform a physical exam to establish the diagnosis and severity of disease, including: • Pallor (e. Laboratory interpretation: Students should be able to recommend when to order diagnostic and laboratory tests and be able to interpret them, both prior to and after initiating treatment based on the differential diagnosis including consideration of test cost and performance characteristics as well as patient preferences. Laboratory and diagnostic tests should include, when appropriate: • Hemoglobin and hematocrit. Communication skills: Students should be able to: • Communicate the diagnosis, treatment plan, and subsequent follow-up to patients. Basic procedural skills: Students should be able to perform and interpret: • Stool occult blood testing. Management skills: Students should be able to develop an appropriate evaluation and treatment plan for patients that includes: • Evaluating for underlying disease processes, given that anemia is not a disease per se, but rather a common finding that requires further delineation in order to identify the underlying cause. Demonstrate commitment to using risk-benefit, cost-benefit, and evidence- based considerations in the selection of diagnostic and therapeutic interventions for anemia. Appreciate the impact anemia has on a patient’s quality of life, well-being, ability to work, and the family. Recognize the importance of and demonstrate a commitment to the utilization of other healthcare professions in the treatment of anemia. It has an important differential diagnosis, and the initial decision-making must be made on the basis of clinical findings. As such, it is an excellent training condition for teaching decision-making based on careful collection and interpretation of basic clinical data. There is emerging data on test utility, especially as regards expensive spinal imaging, which facilitates teaching rational, cost-effective test ordering. Moreover, its requirement for skillful management, patient education, and support facilitate the teaching of these competencies. The symptoms, signs, and typical clinical course of the various causes of back pain including: • Ligamentous/muscle strain (nonspecific musculoskeletal back pain). The role of diagnostic studies in the evaluation of the back pain there indications, limitations, cost: • Plain radiography. Response to therapy of the various etiologies, with understanding of the roles of: • Bed rest. History-taking skills: Students should be able to obtain, document, and present an age-appropriate medical history, that differentiates among etiologies of disease, including: • Cancer history. Physical exam skills: Students should be able to perform a physical exam to establish the diagnosis and severity of disease, including: • Examination of the spine. Laboratory interpretation: Students should be able to recommend when to order diagnostic and laboratory tests and be able to interpret them, both prior to and after initiating treatment based on the differential diagnosis, including consideration of test cost and performance characteristics as well as patient preferences. Communication skills: Students should be able to: • Communicate the diagnosis, treatment plan, and subsequent follow-up to patients. Management skills: Students should able to develop an appropriate evaluation and treatment plan for patients that includes: • Patient education about the typical course of back pain.
Painful vascular occlusive crises typically haemoglobins result from: produce symptoms of bone pain and pleuritic chest pain r Abnormal globin chain production such as thalas- with a low-grade fever discount 50mg zoloft free shipping mood disorder in teens. Other patterns of crisis: r Acute sequestration (pooling of blood in liver and Sickle cell anaemia spleen) requires transfusion for apparent hypo- Deﬁnition volaemia buy zoloft 100mg on line depression test for social security. Autosomal recessive condition in which there is abnor- r Pulmonary infarction may occur in association with mal structure of the globin chain buy zoloft amex anxiety nos code. Chapter 12: Haemoglobin disorders and anaemia 475 Complications syndrome or cerebral infarction require exchange blood Patients have a susceptibility to infections including transfusionstoremovesicklecells. Transfusionsmayalso streptococcal infections and osteomyelitis often due be indicated in patients with regular severe crises and to salmonella. Prognosis Retinal detachment and proliferative retinopathy may Thereismarkedvariationintheseverityofthecondition, result in blindness. See also complications of haemolytic some patients have a relatively normal life span with few anaemia (page 473). Blood ﬁlm shows a α-Thalassaemia high reticulocyte count and sickle shaped red blood cells. Deﬁnition r Sickle screening tests use a reducing solution, which Inherited haemoglobinopathy with defective synthesis causes HbS to precipitate. Aetiology r X-ray of the tubular bones may show destruction and α-Thalassaemia is caused by gene deletions. There are medullary sclerosis together with periosteal bone for- four copies of the α gene, two on each chromosome 16. Management Clinical features Treatment is largely symptomatic with prophylactic an- r Deletion of all four copies of the α gene (–/–) prevents tibiotics,folicacidandpneumococcalvaccination. This disorder agement of a painful crisis includes oxygenation, ade- is also termed haemoglobin Bart’s (γ4)hydrops syn- quate hydration and analgesia. Acute se- r Deletion of three genes (–/α-) causes HbH disease (a questration requires blood transfusion, as patients be- moderate anaemia with splenomegaly and the pro- comeshocked. Normal Investigations Full blood count shows microcytosis with or without Sickle Trait anaemia. These mutations may result in no β chain production Investigations (β0)orveryreducedproduction (β+). The reticulocyte count is noproductionofβ globinandhavetheclinicalpicture raised and there are nucleated red cells. Management Excess α chains precipitate in the red blood cells r Thalassaemiaminordoesnotrequiretreatment;how- or combine with δ resulting in increased HbA2, and ever, iron supplements should be avoided unless γ resulting in increased levels of fetal haemoglobin co-existent iron deﬁciency has been demonstrated. The partners of women with thalassaemia minor r If there are defects in both β and δ genes, patients shouldbescreenedtoallowappropriategeneticcoun- have thalassaemia intermedia (homozygous) or tha- selling. Homozygous combined β, γ and δ are in- r Thalassaemia major and symptomatic thalassaemia compatible with life. This Clinical features aims to suppress ineffective erythropoesis and pre- r Thalassaemia minor/trait is asymptomatic with a vent bony deformity, while allowing normal growth mild hypochromic microcytic anaemia. Iron overload is prevented by the r Thalassaemia intermedia causes symptomatic mod- use of the chelating agent desferrioxamine, which is erate anaemia with splenomegaly. Splenectomy should be considered in patients ure to thrive and recurrent infections. Bone the production of fetal haemoglobin ceases and the marrow transplantation has been used successfully patient becomes symptomatic with a severe anae- in young patients with severe β-thalassaemia major. Extramedullary haemopoesis causes hepato- Other treatments under investigation include gene splenomegaly, maxillary overgrowth and trabecula- therapy and drugs to maintain the production of fetal tion on bone X-rays. Random X inacti- vation (Lyonisation) means that some heterozygous fe- Glucose-6-phosphate dehydrogenase males may also have symptoms. Clinical features With such a wide variety of genes and enzymatic activity, Aetiology aspectrum of clinical conditions occur. Investigations Pathophysiology During an attack the blood ﬁlm may show irregularly IgMorIgG antibodies are produced, which bind to red contracted cells, bite cells (indented membrane), blister cells. Autoimmune haemolytic anaemia Deﬁnition Clinical features Acquired disorders resulting in haemolysis due to red The clinical features, speciﬁc investigations and manage- cell autoantibodies. IgM anti human globulin Red cells coated in antibodies Agglutination (visible) Figure 12. Splenectomy may be indicated if lymphatic leukaemia, haemolysis is severe and carcinoma and drugs such refractory. Cold haemagglutinin May be primary or secondary IgM antibodies agglutinate best Treat any underlying cause and disease to Mycoplasma at 4◦C, often against minor avoid extremes of temperature. Deﬁnition A pancytopenia due to a loss of haematopoetic precur- Investigations sors from the bone marrow. Full blood count and blood ﬁlm will demonstrate a pan- cytopenia with absence of reticulocytes. A bone marrow Aetiology/pathophysiology aspirate and trephine shows a hypocellular marrow with Aplastic anaemia can be either congenital or much more no increased reticulin (ﬁbrosis). This agents, supportive care (blood and platelet transfusions) is an autosomal recessive aplastic anaemia with limb and some form of deﬁnitive therapy. Otherdrugsmaycauseaplasticanaemia Immunosuppressive therapy is used as ﬁrst line treat- through dose dependent (e. Prognosis Clinical features The course is dependent on the severity of the dis- Patients present with the features of pancytopenia: ease and the age of the patient. In the United Kingdom, travellers to these ar- 3year survival but there is a signiﬁcant risk of developing eas who do not take adequate precautions are at greatest paroxysmal nocturnal haemoglobinuria, myelodysplas- risk. Transmission occurs predominantly by the bite of the female Anophe- Deﬁnition les mosquito although transmission may occur by blood Malaria is an infection caused by one of the four species transfusion or transplacentally. Incidence Worldwide there are 300–500 million cases of malaria Pathophysiology peryear with a mortality rate of up to 1%. In the United Parasites consume red cell proteins, glucose and Kingdom there are 1500–2000 cases per year, most of haemoglobin. They affect the red cell membrane making which are caused by Plasmodium falciparum. The inci- the cell less deformable and ultimately causing cell ly- dence in the United Kingdom is rising. Falciparum induces cell surface adhesion molecules on red cells causing adhesion to small vessels and un- Geography infected red cells. This leads to occlusion within the Endemic malaria is found in parts of Asia, Africa, Cen- microcirculation and organ dysfunction. Resistance to tral and South America, Oceania and certain Caribbean malaria is conferred by genetic variation: 1. Fertilisation occurs forming sporozites Sporozoites which migrate to the salivary glands.
Attributes of measurements Measurements should be precise buy cheap zoloft on-line depression test in pregnancy, reliable purchase zoloft 25mg on-line depression vs sadness, accurate buy discount zoloft 50 mg online depression glass defined, and valid. Precision simply means that the measurement is nearly the same value each time it is measured. Statistically it states that for a precise measurement, there is only a small amount of variation around the true value of the variable being measured. In statistical terminology this is equivalent to a small standard deviation or range around the central value of multiple measurements. For example, if each time a physician takes a blood pressure, the same measurement is obtained, then we can say that the measure- ment is precise. The same measurement can become imprecise if not repeated the same way, for example if different blood-pressure cuffs are used. Reliability has been used loosely as a synonym of precision but it also incor- porates durability or reproducibility of the measurement in its deﬁnition. It tells you that no matter how often you repeat the measurement you will get the same or similar result. It can be precise, in which case the results of repeated measure- ments are almost exactly the same. We are looking for instruments that will give precise, consistent, reproducible, and dependable data. Statistically, it is equivalent to saying that the mean or arithmetic average of all measurements taken is the actual and true value of the thing being measured. For example, if indirect blood-pressure measurements use a manometer and blood-pressure cuff that correlate closely to direct intra-arterial measurements in healthy, young volunteers using a pres- sure transducer, it means that the blood pressure measured using the manome- ter and blood-pressure cuff is accurate. The measurement will be inaccurate if the manometer is not calibrated properly or if an incorrect cuff size is used. It is possible for a measurement to be accurate but not precise if the average measured result is the true value of the thing being measured but the spread around that measure is very great. Precision and accuracy are direct functions of the instruments chosen to make a particular measurement. Validity tells us that the measurement actually rep- resents what we want to measure. For example, weight is a less valid measure for obe- sity than skin fold thickness or body mass index. Blood pressure measured with a standard blood-pressure cuff is a valid measure of the intra-arterial pressure. However, a single blood-sugar measurement is not a valid measure of overall diabetic control. The ﬁrst set of deﬁnitions deﬁnes validity by the process with which it is determined. The second deﬁnition deﬁnes where validity is found in a clinical study and includes internal and external validity. This means that there is a study show- ing that the measurement of interest agrees with other accepted measures of the same thing. Similarly, blood-pressure cuff readings correlate with intra-arterial blood pressure as recorded by an electrical pressure transducer. Predictive validity is a type of criterion-based validity that describes how well the measurement predicts an outcome event. This could be the result of another measurement or the presence or absence of a particular outcome. For example, lack of fever in an elderly patient with pneumonia predicts a higher mortality than in the same group of patients with fever. This was determined from studies of factors related to the speciﬁc outcome of mortality in elderly patients with pneumonia. We would say that lack of fever in elderly pneumonia patients gives predictive validity to the outcome of increased mortality. It is a statement of the fact that the instrument measures the phenomenon of interest and that it makes sense. For example, the measured performance of a student on one multiple-choice examination should predict that student’s performance on another multiple-choice examination. Performance on an observed exam- ination of a standardized patient accurately measures the student’s ability to accurately perform a history and physical examination on any patient. However, having face validity doesn’t mean that the measure can be accepted without ver- iﬁcation. In this example, it must be validated because the testing situation may cause some students to freeze up, which they wouldn’t do when face-to-face with a real patient, thus decreasing its face validity. Validity can also be classiﬁed by the potential effect of bias or error on the results of a study. Internal and external validity are the terms used to describe this and are the most common ways to classify validity. Internal validity exists when preci- sion and accuracy are not distorted by bias introduced into a study. Internal valid- ity is threatened by problems in the way a study is designed or carried out, or with the instruments used to make the measurements. External validity exists when the measurement can be generalized and the results extrapolated to other clinical situations or populations. External validity is threatened when the pop- ulation studied is too restrictive and you cannot apply the results to another and usually larger, population. The results of an internally valid study are true if there is no serious source of bias that can Instruments and measurements: precision and validity 75 produce a fatal ﬂaw and invalidate the study. Truth in the universe relating to all other patients with this problem is only present if the study is externally valid. Improving precision and accuracy In the process of designing a study, the researcher should maximize precision, accuracy, and validity. The methods section detailing the protocol used in the study should enable the reader to determine if enough safeguards have been taken to ensure a valid study. The protocol should be explicit and given in enough detail to be reproduced easily by anyone reading the study. There are four possible error patterns that can occur in the process of measur- ing data. Using exactly reproducible and objective measurements, standardizing the performance of the measurements and intensively training the observers will increase precision. Automated instruments can give more reliable measure- ments, assuming that they are regularly calibrated. The number of trained observers should be kept to a minimum to increase precision, since having more observers increases the likelihood that one will make a serious error. For example, tak- ing a blood pressure is obtrusive while simply observing a patient for an out- come like death or living is usually non-obtrusive. Watching someone work and recording his or her efﬁciency is obtrusive since it could result in a change in behavior, called the Hawthorne effect. If the observer is unaware of the group to which the patient is assigned, there is less risk that the measurement will be 76 Essential Evidence-Based Medicine biased. Blinding creates the climate for consistency and fairness in the measure- ments, and results in reduced systematic error.
Governors State University. 2019.