Stress testing

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Stress testing is a form of deliberately intense or thorough testing, used to determine the stability of a given system, critical infrastructure or entity. It involves testing beyond normal operational capacity, often to a breaking point, in order to observe the results.

Contents

Reasons can include:

Reliability engineers often test items under expected stress or even under accelerated stress in order to determine the operating life of the item or to determine modes of failure. [1]

The term "stress" may have a more specific meaning in certain industries, such as material sciences, and therefore stress testing may sometimes have a technical meaning – one example is in fatigue testing for materials.

In animal biology, there are various forms of biological stress and biological stress testing, such as the cardiac stress test in humans, often administered for biomedical reasons. In exercise physiology, training zones are often determined in relation to metabolic stress protocols, quantifying energy production, oxygen uptake, or blood chemistry regimes.

Computing

This section is an excerpt from Stress testing (computing).[ edit ]
In computing, stress testing (sometimes called torture testing) can be applied to either hardware or software. It is used to determine the maximum capability of a computer system and is often used for purposes such as scaling for production use and ensuring reliability and stability. [2] Stress tests typically involve running a large amount of resource-intensive processes until the system either crashes or nearly does so.

Materials

This section is an excerpt from Fatigue testing.[ edit ]
IABG Fatigue test of the Airbus A380 wing (showing the wing deflected upwards superimposed on the unloaded wing). The wing was tested for a total of 47500 flights which is 2.5 times the number of flights in 25 years of operation. Each 16 hour flight took 11 minutes to simulate on the fatigue test rig. IABG Test Setup A380 Dresden bent wing.jpg
IABG Fatigue test of the Airbus A380 wing (showing the wing deflected upwards superimposed on the unloaded wing). The wing was tested for a total of 47500 flights which is 2.5 times the number of flights in 25 years of operation. Each 16 hour flight took 11 minutes to simulate on the fatigue test rig.

Fatigue testing is a specialised form of mechanical testing that is performed by applying cyclic loading to a coupon or structure. These tests are used either to generate fatigue life and crack growth data, identify critical locations or demonstrate the safety of a structure that may be susceptible to fatigue. Fatigue tests are used on a range of components from coupons through to full size test articles such as automobiles and aircraft.

Fatigue tests on coupons are typically conducted using servo hydraulic test machines which are capable of applying large variable amplitude cyclic loads. [4] Constant amplitude testing can also be applied by simpler oscillating machines. The fatigue life of a coupon is the number of cycles it takes to break the coupon. This data can be used for creating stress-life or strain-life curves. The rate of crack growth in a coupon can also be measured, either during the test or afterward using fractography. Testing of coupons can also be carried out inside environmental chambers where the temperature, humidity and environment that may affect the rate of crack growth can be controlled.

Because of the size and unique shape of full size test articles, special test rigs are built to apply loads through a series of hydraulic or electric actuators. Actuators aim to reproduce the significant loads experienced by a structure, which in the case of aircraft, may consist of manoeuvre, gust, buffet and ground-air-ground (GAG) loading. A representative sample or block of loading is applied repeatedly until the safe life of the structure has been demonstrated or failures occur which need to be repaired. Instrumentation such as load cells, strain gauges and displacement gauges are installed on the structure to ensure the correct loading has been applied. Periodic inspections of the structure around critical stress concentrations such as holes and fittings are made to determine the time detectable cracks were found and to ensure any cracking that does occur, does not affect other areas of the test article. Because not all loads can be applied, any unbalanced structural loads are typically reacted out to the test floor through non-critical structure such as the undercarriage.

Airworthiness standards generally require a fatigue test to be carried out for large aircraft prior to certification to determine their safe life. [5] Small aircraft may demonstrate safety through calculations, although typically larger scatter or safety factors are used because of the additional uncertainty involved.

Critical infrastructure

This section is an excerpt from Critical infrastructure § Stress testing.[ edit ]

Critical infrastructure (CI) such as highways, railways, electric power networks, dams, port facilities, major gas pipelines or oil refineries are exposed to multiple natural and human-induced hazards and stressors, including earthquakes, landslides, floods, tsunami, wildfires, climate change effects or explosions. These stressors and abrupt events can cause failures and losses, and hence, can interrupt essential services for the society and the economy. [6] Therefore, CI owners and operators need to identify and quantify the risks posed by the CIs due to different stressors, in order to define mitigation strategies [7] and improve the resilience of the CIs. [8] [9] Stress tests are advanced and standardised tools for hazard and risk assessment of CIs, that include both low-probability high-consequence (LP-HC) events and so-called extreme or rare events, as well as the systematic application of these new tools to classes of CI.

Stress testing is the process of assessing the ability of a CI to maintain a certain level of functionality under unfavourable conditions, while stress tests consider LP-HC events, which are not always accounted for in the design and risk assessment procedures, commonly adopted by public authorities or industrial stakeholders. A multilevel stress test methodology for CI has been developed in the framework of the European research project STREST, [10] consisting of four phases: [11]

Phase 1: Preassessment, during which the data available on the CI (risk context) and on the phenomena of interest (hazard context) are collected. The goal and objectives, the time frame, the stress test level and the total costs of the stress test are defined.

Phase 2: Assessment, during which the stress test at the component and the system scope is performed, including fragility [12] and risk [13] analysis of the CIs for the stressors defined in Phase 1. The stress test can result in three outcomes: Pass, Partly Pass and Fail, based on the comparison of the quantified risks to acceptable risk exposure levels and a penalty system.

Phase 3: Decision, during which the results of the stress test are analyzed according to the goal and objectives defined in Phase 1. Critical events (events that most likely cause the exceedance of a given level of loss) and risk mitigation strategies are identified.

Phase 4: Report, during which the stress test outcome and risk mitigation guidelines based on the findings established in Phase 3 are formulated and presented to the stakeholders.

This stress-testing methodology has been demonstrated to six CIs in Europe at component and system level: [14] an oil refinery and petrochemical plant in Milazzo, Italy; a conceptual alpine earth-fill dam in Switzerland; the Baku–Tbilisi–Ceyhan pipeline in Turkey; part of the Gasunie national gas storage and distribution network in the Netherlands; the port infrastructure of Thessaloniki, Greece; and an industrial district in the region of Tuscany, Italy. The outcome of the stress testing included the definition of critical components and events and risk mitigation strategies, which are formulated and reported to stakeholders.

Finance

This section is an excerpt from Stress test (financial).[ edit ]

In finance, a stress test is an analysis or simulation designed to determine the ability of a given financial instrument or financial institution to deal with an economic crisis. Instead of doing financial projection on a "best estimate" basis, a company or its regulators may do stress testing where they look at how robust a financial instrument is in certain crashes, a form of scenario analysis. They may test the instrument under, for example, the following stresses:

  • What happens if unemployment rate rises to v% in a specific year?
  • What happens if equity markets crash by more than w% this year?
  • What happens if GDP falls by x% in a given year?
  • What happens if interest rates go up by at least y%?
  • What if half the instruments in the portfolio terminate their contracts in the fifth year?
  • What happens if oil prices rise by z%?
  • What happens if there is a polar vortex event in a particular region?

This type of analysis has become increasingly widespread, and has been taken up by various governmental bodies (such as the PRA in the UK or inter-governmental bodies such as the European Banking Authority (EBA) and the International Monetary Fund) as a regulatory requirement on certain financial institutions to ensure adequate capital allocation levels to cover potential losses incurred during extreme, but plausible, events. The EBA's regulatory stress tests have been referred to as "a walk in the park" by Saxo Bank's Chief Economist. [15]

This emphasis on adequate, risk adjusted determination of capital has been further enhanced by modifications to banking regulations such as Basel II. Stress testing models typically allow not only the testing of individual stressors, but also combinations of different events. There is also usually the ability to test the current exposure to a known historical scenario (such as the Russian debt default in 1998 or 9/11 attacks) to ensure the liquidity of the institution. In 2014, 25 banks failed in a stress test conducted by EBA.

Medical

Cardiac

This section is an excerpt from Cardiac stress test.[ edit ]

A cardiac stress test is a cardiological examination that evaluates the cardiovascular system's response to external stress within a controlled clinical setting. This stress response can be induced through physical exercise (usually a treadmill) or intravenous pharmacological stimulation of heart rate. [16]

As the heart works progressively harder (stressed) it is monitored using an electrocardiogram (ECG) monitor. This measures the heart's electrical rhythms and broader electrophysiology. Pulse rate, blood pressure and symptoms such as chest discomfort or fatigue are simultaneously monitored by attending clinical staff. Clinical staff will question the patient throughout the procedure asking questions that relate to pain and perceived discomfort. Abnormalities in blood pressure, heart rate, ECG or worsening physical symptoms could be indicative of coronary artery disease. [17]

Stress testing does not accurately diagnose all cases of coronary artery disease, and can often indicate that it exists in people who do not have the condition. The test can also detect heart abnormalities such as arrythmias, and conditions affecting electrical conduction within the heart such as various types of fascicular blocks. [18]

A "normal" stress test does not offer any substantial reassurance that a future unstable coronary plaque will not rupture and block an artery, inducing a heart attack. As with all medical diagnostic procedures, data is only from a moment in time. A primary reason stress testing is not perceived as a robust method of CAD detection — is that stress testing generally only detects arteries that are severely narrowed (~70% or more). [19] [20] [21]

Childbirth

This section is an excerpt from Contraction stress test.[ edit ]

A contraction stress test (CST) is performed near the end of pregnancy (34 weeks' gestation) to determine how well the fetus will cope with the contractions of childbirth. The aim is to induce contractions and monitor the fetus to check for heart rate abnormalities using a cardiotocograph. A CST is one type of antenatal fetal surveillance technique.

During uterine contractions, fetal oxygenation is worsened. Late decelerations in fetal heart rate occurring during uterine contractions are associated with increased fetal death rate, growth retardation and neonatal depression. [22] [23] This test assesses fetal heart rate in response to uterine contractions via electronic fetal monitoring. Uterine activity is monitored by tocodynamometer. [24]

See also

Related Research Articles

<span class="mw-page-title-main">Coronary artery disease</span> Reduction of blood flow to the heart

Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the cardiac muscle due to build-up of atherosclerotic plaque in the arteries of the heart. It is the most common of the cardiovascular diseases. Types include stable angina, unstable angina, and myocardial infarction.

<span class="mw-page-title-main">Angina</span> Chest discomfort due to disorder of the heart muscles

Angina, also known as angina pectoris, is chest pain or pressure, usually caused by insufficient blood flow to the heart muscle (myocardium). It is most commonly a symptom of coronary artery disease.

<span class="mw-page-title-main">Heart rate</span> Speed of the heartbeat, measured in beats per minute

Heart rate is the frequency of the heartbeat measured by the number of contractions of the heart per minute. The heart rate varies according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide. It is also modulated by numerous factors, including genetics, physical fitness, stress or psychological status, diet, drugs, hormonal status, environment, and disease/illness, as well as the interaction between these factors. It is usually equal or close to the pulse rate measured at any peripheral point.

<span class="mw-page-title-main">Fatigue (material)</span> Initiation and propagation of cracks in a material due to cyclic loading

In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of the fracture surface. The crack will continue to grow until it reaches a critical size, which occurs when the stress intensity factor of the crack exceeds the fracture toughness of the material, producing rapid propagation and typically complete fracture of the structure.

<span class="mw-page-title-main">Critical infrastructure</span> Infrastructure important to national security

Critical infrastructure, or critical national infrastructure (CNI) in the UK, describes infrastructure considered essential by governments for the functioning of a society and economy and deserving of special protection for national security. Critical infrastructure has traditionally been viewed as under the scope of government due to its strategic importance, yet there's an observable trend towards its privatization, raising discussions about how the private sector can contribute to these essential services.

<span class="mw-page-title-main">Cardiotocography</span> Technical means of recording the fetal heartbeat and the uterine contractions during pregnancy

Cardiotocography (CTG) is a technique used to monitor the fetal heartbeat and uterine contractions during pregnancy and labour. The machine used to perform the monitoring is called a cardiotocograph.

<span class="mw-page-title-main">Cardiac stress test</span> Measures the hearts ability to respond to external stress in a controlled clinical environment

A cardiac stress test is a cardiological examination that evaluates the cardiovascular system's response to external stress within a controlled clinical setting. This stress response can be induced through physical exercise or intravenous pharmacological stimulation of heart rate.

A vulnerable plaque is a kind of atheromatous plaque – a collection of white blood cells and lipids in the wall of an artery – that is particularly unstable and prone to produce sudden major problems such as a heart attack or stroke.

Vasospasm refers to a condition in which an arterial spasm leads to vasoconstriction. This can lead to tissue ischemia and tissue death (necrosis). Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to post-operative stroke and death especially after aneurysmal subarachnoid hemorrhage. Vasospasm typically appears 4 to 10 days after subarachnoid hemorrhage.

A nonstress test (NST) is a screening test used in pregnancy to assess fetal status by means of the fetal heart rate and its responsiveness. A cardiotocograph is used to monitor the fetal heart rate and presence or absence of uterine contractions. The test is typically termed "reactive" or "nonreactive".

A contraction stress test (CST) is performed near the end of pregnancy to determine how well the fetus will cope with the contractions of childbirth. The aim is to induce contractions and monitor the fetus to check for heart rate abnormalities using a cardiotocograph. A CST is one type of antenatal fetal surveillance technique.

Coronary vasospasm refers to when a coronary artery suddenly undergoes either complete or sub-total temporary occlusion.

<span class="mw-page-title-main">Myocardial perfusion imaging</span> Nuclear medicine imaging method

Myocardial perfusion imaging or scanning is a nuclear medicine procedure that illustrates the function of the heart muscle (myocardium).

The complications of prolonged standing are conditions that may arise after standing, walking, or running for prolonged periods. Many of the complications come from prolonged standing that is repeated several times a week. Many jobs require prolonged standing, such as "retail staff, baristas, bartenders, assembly line workers, security staff, engineers, catering staff, library assistants, hair stylists and laboratory technicians". The basic physiological change that occurs in the body during prolonged standing or sudden stand from supine position is that there will be increased pooling of blood in the legs. This decreases the venous return, and so there will be decreased cardiac output, which ultimately causes systolic blood pressure to fall (hypotension). This hypotension may lead the subject to faint or to have other symptoms of hypotension. Standing requires about 10% more energy than sitting.

<span class="mw-page-title-main">Coronary ischemia</span> Medical condition

Coronary ischemia, myocardial ischemia, or cardiac ischemia, is a medical term for abnormally reduced blood flow in the coronary circulation through the coronary arteries. Coronary ischemia is linked to heart disease, and heart attacks. Coronary arteries deliver oxygen-rich blood to the heart muscle. Reduced blood flow to the heart associated with coronary ischemia can result in inadequate oxygen supply to the heart muscle. When oxygen supply to the heart is unable to keep up with oxygen demand from the muscle, the result is the characteristic symptoms of coronary ischemia, the most common of which is chest pain. Chest pain due to coronary ischemia commonly radiates to the arm or neck. Certain individuals such as women, diabetics, and the elderly may present with more varied symptoms. If blood flow through the coronary arteries is stopped completely, cardiac muscle cells may die, known as a myocardial infarction, or heart attack.

<span class="mw-page-title-main">Myocardial infarction</span> Interruption of cardiac blood supply

A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops in one of the coronary arteries of the heart, causing infarction to the heart muscle. The most common symptom is retrosternal chest pain or discomfort that classically radiates to the left shoulder, arm, or jaw. The pain may occasionally feel like heartburn.

<span class="mw-page-title-main">Myocardial bridge</span> Birth defect of a coronary artery through the heart muscle

A myocardial bridge (MB) is a common congenital heart anomaly in which one of the coronary arteries tunnels through the heart muscle (myocardium) itself.

<span class="mw-page-title-main">Cardiac magnetic resonance imaging perfusion</span>

Cardiac magnetic resonance imaging perfusion, also known as stress CMR perfusion, is a clinical magnetic resonance imaging test performed on patients with known or suspected coronary artery disease to determine if there are perfusion defects in the myocardium of the left ventricle that are caused by narrowing of one or more of the coronary arteries.

<span class="mw-page-title-main">Prolonged labor</span> Medical condition

Prolonged labor is the inability of a woman to proceed with childbirth upon going into labor. Prolonged labor typically lasts over 20 hours for first time mothers, and over 14 hours for women that have already had children. Failure to progress can take place during two different phases; the latent phase and active phase of labor. The latent phase of labor can be emotionally tiring and cause fatigue, but it typically does not result in further problems. The active phase of labor, on the other hand, if prolonged, can result in long term complications.

<span class="mw-page-title-main">Fatigue testing</span> Determination of a material or structures resiliency against cyclic loading

Fatigue testing is a specialised form of mechanical testing that is performed by applying cyclic loading to a coupon or structure. These tests are used either to generate fatigue life and crack growth data, identify critical locations or demonstrate the safety of a structure that may be susceptible to fatigue. Fatigue tests are used on a range of components from coupons through to full size test articles such as automobiles and aircraft.

References

  1. ↑ Nelson, Wayne B., (2004), Accelerated Testing - Statistical Models, Test Plans, and Data Analysis, John Wiley & Sons, New York, ISBN   0-471-69736-2
  2. ↑ "Keep it stable, stupid! How to stress-test your PC hardware". PCWorld. Retrieved 2023-03-11.
  3. ↑ "Test programme and certification" . Retrieved 2020-02-27.
  4. ↑ "High-Rate Test Systems" (PDF). MTS. Retrieved 26 June 2019.
  5. ↑ "FAA PART 23—Airworthiness Standards: Normal Category Airplanes" . Retrieved 26 June 2019.
  6. ↑ Pescaroli, Gianluca; Alexander, David (2016-05-01). "Critical infrastructure, panarchies and the vulnerability paths of cascading disasters". Natural Hazards. 82 (1): 175–192. Bibcode:2016NatHa..82..175P. doi: 10.1007/s11069-016-2186-3 . ISSN   1573-0840.
  7. ↑ Mignan, A.; Karvounis, D.; Broccardo, M.; Wiemer, S.; Giardini, D. (March 2019). "Including seismic risk mitigation measures into the Levelized Cost Of Electricity in enhanced geothermal systems for optimal siting". Applied Energy. 238: 831–850. Bibcode:2019ApEn..238..831M. doi: 10.1016/j.apenergy.2019.01.109 . hdl: 20.500.11850/322346 .
  8. ↑ Linkov, Igor; Bridges, Todd; Creutzig, Felix; Decker, Jennifer; Fox-Lent, Cate; Kröger, Wolfgang; Lambert, James H.; Levermann, Anders; Montreuil, Benoit; Nathwani, Jatin; Nyer, Raymond (June 2014). "Changing the resilience paradigm". Nature Climate Change. 4 (6): 407–409. Bibcode:2014NatCC...4..407L. doi:10.1038/nclimate2227. ISSN   1758-6798. S2CID   85351884.
  9. ↑ Argyroudis, Sotirios A.; Mitoulis, Stergios A.; Hofer, Lorenzo; Zanini, Mariano Angelo; Tubaldi, Enrico; Frangopol, Dan M. (April 2020). "Resilience assessment framework for critical infrastructure in a multi-hazard environment: Case study on transport assets" (PDF). Science of the Total Environment. 714: 136854. Bibcode:2020ScTEn.714m6854A. doi:10.1016/j.scitotenv.2020.136854. PMID   32018987. S2CID   211036128.
  10. ↑ "STREST-Harmonized approach to stress tests for critical infrastructures against natural hazards. Funded from the European Union's Seventh Framework Programme FP7/2007-2013, under grant agreement no. 603389. Project Coordinator: Domenico Giardini; Project Manager: Arnaud Mignan, ETH Zurich".
  11. ↑ Esposito Simona; Stojadinović Božidar; Babič Anže; Dolšek Matjaž; Iqbal Sarfraz; Selva Jacopo; Broccardo Marco; Mignan Arnaud; Giardini Domenico (2020-03-01). "Risk-Based Multilevel Methodology to Stress Test Critical Infrastructure Systems". Journal of Infrastructure Systems. 26 (1): 04019035. doi:10.1061/(ASCE)IS.1943-555X.0000520. S2CID   214354801.
  12. ↑ Pitilakis, K.; Crowley, H.; Kaynia, A.M., eds. (2014). SYNER-G: Typology Definition and Fragility Functions for Physical Elements at Seismic Risk. Geotechnical, Geological and Earthquake Engineering. Vol. 27. Dordrecht: Springer Netherlands. doi:10.1007/978-94-007-7872-6. ISBN   978-94-007-7871-9. S2CID   133078584.
  13. ↑ Pitilakis, K.; Franchin, P.; Khazai, B.; Wenzel, H., eds. (2014). SYNER-G: Systemic Seismic Vulnerability and Risk Assessment of Complex Urban, Utility, Lifeline Systems and Critical Facilities. Geotechnical, Geological and Earthquake Engineering. Vol. 31. Dordrecht: Springer Netherlands. doi:10.1007/978-94-017-8835-9. ISBN   978-94-017-8834-2. S2CID   107566163.
  14. ↑ Argyroudis, Sotirios A.; Fotopoulou, Stavroula; Karafagka, Stella; Pitilakis, Kyriazis; Selva, Jacopo; Salzano, Ernesto; Basco, Anna; Crowley, Helen; Rodrigues, Daniela; Matos, José P.; Schleiss, Anton J. (2020). "A risk-based multi-level stress test methodology: application to six critical non-nuclear infrastructures in Europe" (PDF). Natural Hazards. 100 (2): 595–633. Bibcode:2020NatHa.100..595A. doi:10.1007/s11069-019-03828-5. hdl:11585/711534. ISSN   1573-0840. S2CID   209432723.
  15. ↑ Cosgrave, Jenny (Oct 27, 2014). "Central bankers back stress tests as criticism swirls". CNBC. Retrieved March 5, 2015.
  16. ↑ "Stress Tests: MedlinePlus Medical Test". medlineplus.gov. Retrieved 2023-11-09.
  17. ↑ "Exercise ECG". British Heart Foundation. Retrieved 2023-11-09.
  18. ↑ Ladapo, Joseph A.; Blecker, Saul; O'Donnell, Michael; Jumkhawala, Saahil A.; Douglas, Pamela S. (2016-08-18). "Appropriate Use of Cardiac Stress Testing with Imaging: A Systematic Review and Meta-Analysis". PLOS ONE. 11 (8): e0161153. Bibcode:2016PLoSO..1161153L. doi: 10.1371/journal.pone.0161153 . ISSN   1932-6203. PMC   4990235 . PMID   27536775.
  19. ↑ Vilcant, Viliane; Zeltser, Roman (2023), "Treadmill Stress Testing", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   29763078 , retrieved 2023-11-09
  20. ↑ Schoenhagen, Paul; Ziada, Khaled M.; Kapadia, Samir R.; Crowe, Timothy D.; Nissen, Steven E.; Tuzcu, E. Murat (2000-02-15). "Extent and Direction of Arterial Remodeling in Stable Versus Unstable Coronary Syndromes: An Intravascular Ultrasound Study". Circulation. 101 (6): 598–603. doi: 10.1161/01.CIR.101.6.598 . ISSN   0009-7322. PMID   10673250.
  21. ↑ Steeds, Richard P; Wheeler, Richard; Bhattacharyya, Sanjeev; Reiken, Joseph; Nihoyannopoulos, Petros; Senior, Roxy; Monaghan, Mark J; Sharma, Vishal (2019-03-28). "Stress echocardiography in coronary artery disease: a practical guideline from the British Society of Echocardiography". Echo Research and Practice. 6 (2): G17–G33. doi:10.1530/ERP-18-0068. ISSN   2055-0464. PMC   6477657 . PMID   30921767.
  22. ↑ Ronald S. Gibbs; et al., eds. (2008). Danforth's obstetrics and gynecology (10th ed.). Philadelphia: Lippincott Williams & Wilkins. p. 161. ISBN   9780781769372.
  23. ↑ Alan H. DeCherney; T. Murphy Goodwin; et al., eds. (2007). Current diagnosis & treatment : Obstetrics & gynecology (10th ed.). New York: McGraw-Hill. pp.  255. ISBN   978-0-07-143900-8.
  24. ↑ III, Frances Talaska Fischbach, Marshall Barnett Dunning (2009). A manual of laboratory and diagnostic tests (8th ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. pp. 1030–31. ISBN   9780781771948.{{cite book}}: CS1 maint: multiple names: authors list (link)
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