In chemistry , the mass concentration ρ i (or γ i ) is defined as the mass of a constituent m i divided by the volume of the mixture V .
34-456: Typhidot is a medical test consisting of a dot ELISA kit that detects IgM and IgG antibodies against the outer membrane protein (OMP) of the Salmonella typhi . The typhidot test becomes positive within 2–3 days of infection and separately identifies IgM and IgG antibodies. The test is based on the presence of specific IgM and IgG antibodies to a specific 50 Kd OMP antigen , which
68-438: A binary classification , with resultant ability to perform bayesian probability and performance metrics of tests, including calculations of sensitivity and specificity . Tests whose results are of continuous values, such as most blood values , can be interpreted as they are, or they can be converted to a binary ones by defining a cutoff value , with test results being designated as positive or negative depending on whether
102-434: A medical setting . Medical tests can be classified by their purposes, including diagnosis, screening or monitoring. A diagnostic test is a procedure performed to confirm or determine the presence of disease in an individual suspected of having a disease, usually following the report of symptoms, or based on other medical test results. This includes posthumous diagnosis . Examples of such tests are: Screening refers to
136-405: A positive test , and a test that indicated absence of a symptom or sign is designated a negative test, as further detailed in a separate section below.A quantification of a target substance, a cell type or another specific entity is a common output of, for example, most blood tests . This is not only answering if a target entity is present or absent, but also how much is present. In blood tests,
170-405: A post-test probability of a condition or other entity. Most diagnostic tests basically use a reference group to establish performance data such as predictive values , likelihood ratios and relative risks , which are then used to interpret the post-test probability for an individual. In monitoring tests of an individual, the test results from previous tests on that individual may be used as
204-404: A decision whether a medical test should be performed or not included: cost of the test, availability of additional tests, potential interference with subsequent test (such as an abdominal palpation potentially inducing intestinal activity whose sounds interfere with a subsequent abdominal auscultation ), time taken for the test or other practical or administrative aspects. The possible benefits of
238-408: A detecting or quantifying test versus rather descriptive information of an individual. For example, questions regarding the occupation or social life of an individual may be regarded as tests that can be regarded as positive or negative for the presence of various risk factors, or they may be regarded as "merely" descriptive, although the latter may be at least as clinically important. The result of
272-537: A diagnostic test may also be weighed against the costs of unnecessary tests and resulting unnecessary follow-up and possibly even unnecessary treatment of incidental findings. In some cases, tests being performed are expected to have no benefit for the individual being tested. Instead, the results may be useful for the establishment of statistics in order to improve health care for other individuals. Patients may give informed consent to undergo medical tests that will benefit other people. In addition to considerations of
306-452: A medical decision. Medical tests are indicated when the information they produce will be used. For example, a screening mammogram is not indicated (not medically appropriate) for a woman who is dying, because even if breast cancer is found, she will die before any cancer treatment could begin. In a simplified fashion, how much a test is indicated for an individual depends largely on its net benefit for that individual. Tests are chosen when
340-734: A medical test or series of tests used to detect or predict the presence of disease in at-risk individuals within a defined group such as a population, family, or workforce. Screenings may be performed to monitor disease prevalence, manage epidemiology, aid in prevention, or strictly for statistical purposes. Examples of screenings include measuring the level of TSH in the blood of a newborn infant as part of newborn screening for congenital hypothyroidism , checking for Lung cancer in non-smoking individuals who are exposed to second-hand smoke in an unregulated working environment, and Pap smear screening for prevention or early detection of cervical cancer . Some medical tests are used to monitor
374-412: A middle-aged person. However, if the same test was performed on that person very recently, then the existence of the previous test is a contraindication for the test (a medically valid reason to not perform it). Information bias is the cognitive bias that causes healthcare providers to order tests that produce information that they do not realistically expect or intend to use for the purpose of making
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#1732772096058408-410: A pure component (mass concentration of single component mixtures) is: where ρ i is the density of the pure component, V i the volume of the pure component before mixing. Specific volume is the inverse of mass concentration only in the case of pure substances, for which mass concentration is the same as the density of the pure-substance: The conversion to molar concentration c i
442-445: A reference to interpret subsequent tests. Some medical testing procedures have associated health risks, and even require general anesthesia , such as the mediastinoscopy . Other tests, such as the blood test or pap smear have little to no direct risks. Medical tests may also have indirect risks , such as the stress of testing, and riskier tests may be required as follow-up for a (potentially) false positive test result. Consult
476-459: A test aimed at detection of an entity may be positive or negative : this has nothing to do with a bad prognosis , but rather means that the test worked or not, and a certain parameter that was evaluated was present or not. For example, a negative screening test for breast cancer means that no sign of breast cancer could be found (which is in fact very positive for the patient). The classification of tests into either positive or negative gives
510-410: Is available. Mass concentration (chemistry) For a pure chemical the mass concentration equals its density (mass divided by volume); thus the mass concentration of a component in a mixture can be called the density of a component in a mixture. This explains the usage of ρ (the lower case Greek letter rho ), the symbol most often used for density. The volume V in the definition refers to
544-443: Is because of many biological solutions being dilute and water-based, an aqueous solution . Liquid water has a density of approximately 1 g/cm (1 g/mL). Thus 100 mL of water is equal to approximately 100 g. Therefore, a solution with 1 g of solute dissolved in final volume of 100 mL aqueous solution may also be considered 1% m/m (1 g solute in 99 g water). This approximation breaks down as
578-495: Is commonly encountered as the ratio of mass/[volume solution], or m/v. In water solutions containing relatively small quantities of dissolved solute (as in biology), such figures may be "percentivized" by multiplying by 100 a ratio of grams solute per mL solution. The result is given as "mass/volume percentage". Such a convention expresses mass concentration of 1 gram of solute in 100 mL of solution, as "1 m/v %". The relation between mass concentration and density of
612-482: Is g/mL; 1 g of water has a volume of approximately 1 mL (at standard temperature and pressure) and the mass concentration is said to be 100%. To make 10 mL of an aqueous 1% cholate solution, 0.1 grams of cholate are dissolved in 10 mL of water. Volumetric flasks are the most appropriate piece of glassware for this procedure as deviations from ideal solution behavior can occur with high solute concentrations. In solutions, mass concentration
646-402: Is impregnated on nitrocellulose strips. IgM shows recent infection whereas IgG signifies remote infection. The most important limitation of this test is that it is not quantitative and result is only positive or negative hhj8b . Whereas a detailed Widal test can tell the titres of specific antibodies. However both tests lack sensitivity and specificity. The Widal test is losing its value as it
680-584: Is labor-intensive and time-consuming. It is an immunochromatographic test. This medical diagnostic article is a stub . You can help Misplaced Pages by expanding it . Medical test A medical test is a medical procedure performed to detect , diagnose , or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging , genetic testing, chemical and cellular analysis, relating to clinical chemistry and molecular diagnostics , are typically performed in
714-548: Is mathematically flawed because the unit " % " can only be used for dimensionless quantities. "Percent solution" or "percentage solution" are thus terms best reserved for "mass percent solutions" (m/m = m% = mass solute/mass total solution after mixing), or "volume percent solutions" (v/v = v% = volume solute per volume of total solution after mixing). The very ambiguous terms "percent solution" and "percentage solutions" with no other qualifiers, continue to occasionally be encountered. This common usage of % to mean m/v in biology
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#1732772096058748-403: Is the mass concentration at a reference temperature, α is the thermal expansion coefficient of the mixture. The sum of the mass concentrations of all components (including the solvent) gives the density ρ of the solution: Thus, for pure component the mass concentration equals the density of the pure component. The SI-unit for mass concentration is kg/m ( kilogram / cubic metre ). This
782-542: Is the same as mg / mL and g/L. Another commonly used unit is g/(100 mL), which is identical to g/dL ( gram / decilitre ). In biology and medicine , the " % " symbol is widely used in a misnomer sense to denote mass concentration, also called "mass/volume percentage". A solution with 1 g of solute dissolved in a final volume of 100 mL of solution would be labeled as "1%" or "1% m/v" (mass/volume). The common names of intravenous sugar solutions, such as D5W and D50W , reflect this convention. The notation
816-423: The expected benefit is greater than the expected harm. The net benefit may roughly be estimated by: b n = Δ p × r i × ( b i − h i ) − h t {\displaystyle b_{n}=\Delta p\times r_{i}\times (b_{i}-h_{i})-h_{t}} , where: Some additional factors that influence
850-432: The health care provider (including physicians , physician assistants , and nurse practitioners ) prescribing any test for further information. Each test has its own indications and contraindications. An indication is a valid medical reason to perform the test. A contraindication is a valid medical reason not to perform the test. For example, a basic cholesterol test may be indicated (medically appropriate) for
884-415: The hope of turning something up to give the doctor a clue as to the nature of a given condition; and imaging tests are subject to fallible human interpretation and can show "incidentalomas" , most of which "are benign, will never cause symptoms, and do not require further evaluation," although clinicians are developing guidelines for deciding when to pursue diagnoses of incidentalomas. The QUADAS-2 revision
918-427: The mass density of a component in the solution), but it can be a source of confusion especially when they appear in the same formula undifferentiated by an additional symbol (like a star superscript, a bolded symbol or varrho ). Mass concentration depends on the variation of the volume of the solution due mainly to thermal expansion. On small intervals of temperature the dependence is : where ρ i ( T 0 )
952-446: The nature of medical testing noted above, other realities can lead to misconceptions and unjustified expectations among patients. These include: Different labs have different normal reference ranges; slightly different values will result from repeating a test; "normal" is defined by a spectrum along a bell curve resulting from the testing of a population, not by "rational, science-based, physiological principles"; sometimes tests are used in
986-402: The progress of, or response to medical treatment . Most test methods can be classified into one of the following broad groups: In vitro tests can be classified according to the location of the sample being tested, including: Tests performed in a physical examination are usually aimed at detecting a symptom or sign , and in these cases, a test that detects a symptom or sign is designated
1020-412: The quantification is relatively well specified, such as given in mass concentration , while most other tests may be quantifications as well although less specified, such as a sign of being "very pale " rather than "slightly pale". Similarly, radiologic images are technically quantifications of radiologic opacity of tissues. Especially in the taking of a medical history , there is no clear limit between
1054-441: The resultant value is higher or lower than the cutoff. In the finding of a pathognomonic sign or symptom it is almost certain that the target condition is present, and in the absence of finding a sine qua non sign or symptom it is almost certain that the target condition is absent. In reality, however, the subjective probability of the presence of a condition is never exactly 100% or 0%, so tests are rather aimed at estimating
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1088-417: The solubility of the dense salt KI is extremely high in water, and the resulting solution is very dense (1.72 times as dense as water). Although there are examples to the contrary, it should be stressed that the commonly used "units" of % w/v are grams per millilitre (g/mL). 1% m/v solutions are sometimes thought of as being gram/100 mL but this detracts from the fact that % m/v
1122-447: The solute concentration is increased (for example, in water–NaCl mixtures ). High solute concentrations are often not physiologically relevant, but are occasionally encountered in pharmacology, where the mass per volume notation is still sometimes encountered. An extreme example is saturated solution of potassium iodide (SSKI) which attains 100 "%" m/v potassium iodide mass concentration (1 gram KI per 1 mL solution) only because
1156-424: The volume of the solution, not the volume of the solvent . One litre of a solution usually contains either slightly more or slightly less than 1 litre of solvent because the process of dissolution causes volume of liquid to increase or decrease. Sometimes the mass concentration is called titre . The notation common with mass density underlines the connection between the two quantities (the mass concentration being
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