Persius/hicric huggingface dataset:
Negative predictive value
Assistant Editor(s)-In-Chief: Kristin Feeney, B.S.

# Overview
The negative predictive value is the proportion of individuals without preclinical disease who test negative using the specified testing modality.

# Worked example

# Definition
The Negative Predictive Value can be defined as:
 NPV = \frac{\rm number\ of\ True\ Negatives}{{\rm number\ of\ True\ Negatives}+{\rm number\ of\ False\ Negatives}}
-r, alternatively,
 NPV = \frac{({\rm specficity}) ({\rm 1 - prevalence})}{({\rm specificity}) ({\rm 1 - prevalence}) + (1 - {\rm sensitivity}) ({\rm prevalence})} 

# Related Chapters
- Positive predictive value
- Binary classification
Nafcillin sodium warnings

# Warnings
Serious and occasionally fatal hypersensitivity (anaphylactic) reactions have been reported in patients on penicillin therapy. These reactions are more likely to occur in individuals with a history of penicillin hypersensitivity and/or a history of sensitivity to multiple allergens. There have been reports of individuals with a history of penicillin hypersensitivity who have experienced severe reactions when treated with cephalosporins. Before initiating therapy with nafcillin, careful inquiry should be made concerning previous hypersensitivity reactions to penicillins, cephalosporins, or other allergens. If an allergic reaction occurs, nafcillin should be discontinued and appropriate therapy instituted. Serious anaphylactic reactions require immediate emergency treatment with epinephrine. Oxygen, intravenous steroids, and airway management, including intubation, should also be administered as indicated.
Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including nafcillin for injection, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.
If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.
Narcissus pseudonarcissus
Narcissus pseudonarcissus (known as the Wild daffodil) is a perennial flowering plant of the family Amaryllidaceae which grows from a bulb. It has pale yellow flowers with a darker central trumpet. The long, narrow leaves are slightly greyish in colour and rise from the base of the stem.
The species is native to Western Europe from Spain and Portugal east to Germany and north to England and Wales. It is commonly grown in gardens and populations have become established in many other parts of Europe. Wild plants grow in woods, grassland and on rocky ground. In Britain native populations have decreased substantially since the 19th century due to intensification of agriculture, clearance of woodland and uprooting of the bulbs for use in gardens.
There are a number of subspecies of the wild daffodil but the exact number varies according to different authors. The large number of cultivars adds to the difficulty of classifation. Among the subspecies is the Tenby daffodil (N. p. ssp. obvallaris, sometimes classed as a separate species) which probably originated in cultivation but now grows wild in south-west Wales.
cy:Cenhinen Bedr
da:Paskelilje
de:Gelbe Narzisse
nl:Wilde narcis
sv:Pasklilja
Nasal Congestion overview
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# Overview
Nasal congestion is the blockage of the nasal passages usually due to membranes lining the nose becoming swollen from inflamed blood vessels.  It is also known as nasal blockage, nasal obstruction, blocked nose, runny nose, and stuffy nose.

# Pathophysiology
Many people think that a nose gets congested (stuffy) from too much thick mucus. However, in most cases, the nose becomes congested when the tissues lining it become swollen. The swelling is due to inflamed blood vessels.

# Diagnosis

## X ray
X-rays of the sinuses and chest x-ray

## CT
CT scan of sinuses are required in some patients to make the diagnosis.
Neotyphodium coenophialum
Neotyphodium coenophialum is a systemic and seed-transmissible symbiont (endophyte) of Lolium arundinaceum (=Festuca arundinacea; tall fescue), a grass endemic to Eurasia and North Africa, but widely naturalized in North America, Australia and New Zealand / Aotearoa. The endophyte has been identified as the cause of the "fescue toxicosis" syndrome sometimes suffered by livestock that graze the N. coenophialum-infected grass. Possible symptoms include poor weight gain, elevated body temperature, reduced conception rates, agalactia, rough hair coat, fat necrosis, loss of switch and ear tips, and lameness or dry gangrene of the feet. Because of the resemblance to symptoms of ergotism in humans, the most likely agents responsible for fescue toxicosis are thought to be the ergot alkaloids produced by N. coenophialum. 
Continued popularity of tall fescue with this endophyte, despite episodic livestock toxicosis, is attributable to the exceptional productivity and stress tolerance of the grass in pastures and hay fields. The endophyte enhances several of these characteristics, including drought tolerance, nitrogen utilization, phosphate acquisition, and resistance to nematodes. Recently, natural strains of N. coenophialum with little or no ergot alkaloid production have been introduced into tall fescue for new cultivar development. These strains are apparently not toxic to livestock, and also provide some, but not necessarily all, of the benefits attributable to the "common toxic" strains in the older tall fescue cultivars. 
Molecular phylogenetic analysis indicates that N. coenophialum is an interspecific hybrid with three ancestors: Epichloe festucae, Epichloe typhina and an undescribed or extinct Neotyphodium species that also contributed a genome to the hybrid endophyte Neotyphodium occultans, among others.
Nephrocalcinosis overview

# Overview
Nephrocalcinosis is a term originally used to describe deposition of calcium salts in the renal parenchyma due to hyperparathyroidism. It is now more commonly used to describe diffuse, fine, renal parenchymal calcification on radiology. During its early stages, nephrocalcinosis is visible on x-ray, and appears as a fine granular mottling over the renal outlines. These outlines eventually come together to form a dense mass.
It is most commonly seen as an incidental finding with medullary sponge kidney on an abdominal x-ray.
However, it may be severe enough to cause (as well as be caused by) renal tubular acidosis or even end stage renal failure, due to disruption of the renal tissue by the deposited calcium.
Nested case-control study
In the nested case-control study, cases of a disease that occur in a defined cohort are identified and, for each, a specified number of matched controls is selected from among those in the cohort who have not developed the disease by the time of disease occurrence in the case. For many research questions, the nested case-control design potentially offers impressive reductions in costs and efforts of data collection and analysis compared with the full cohort approach, with relatively minor loss in statistical efficiency. The nested case-control design is particularly advantageous for studies of biologic precursors of disease. To advance its prevention research agenda, NIH might be encouraged to maintain a registry of new and existing cohorts, with an inventory of data collected for each; to foster the development of specimen banks; and to serve as a clearinghouse for information about optimal storage conditions for various types of specimens.
Compared with case-control studies, nested case-control studies can reduce 'recall bias' and temporal ambiguity, and compared with cohort studies can reduce cost and save time.
The drawback of nested case-control studies is non-diseased persons from whom the controls are selected may not be fully representative of the original cohort, due to death or failure to follow-up cases.

# Similar terms
- Panel study
A case-control study in which cases and controls are drawn from within a prospective study. All cases who developed the outcome of interest during the follow-up are selected and compared with a subgroup of the non-cases. Exposure is defined prior to disease development based on data collected at baseline or on assays conducted in biological samples collected at baseline.
Nitazoxanide microbiology

# Microbiology

## Mechanism of Action
The antiprotozoal activity of nitazoxanide is believed to be due to interference with the pyruvate:ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reaction which is essential to anaerobic energy metabolism. Studies have shown that the PFOR enzyme from Giardia lamblia directly reduces nitazoxanide by transfer of electrons in the absence of ferredoxin. The DNA-derived PFOR protein sequence of Cryptosporidium parvum appears to be similar to that of Giardia lamblia. Interference with the PFOR enzyme-dependent electron transfer reaction may not be the only pathway by which nitazoxanide exhibits antiprotozoal activity.

## Activity in vitro
Nitazoxanide and its metabolite, tizoxanide, are active in vitro in inhibiting the growth of (i) sporozoites and oocysts of Cryptosporidium parvum and (ii) trophozoites of Giardia lamblia (iii) Entamoeba histolytica.

## Drug Resistance
A potential for development of resistance by Cryptosporidium parvum or Giardia lamblia to nitazoxanide has not been examined.

## Susceptibility Tests
For protozoa such as Cryptosporidium parvum and Giardia lamblia, standardized tests for use in clinical microbiology laboratories are not available
Nocturnal asthma overview
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# Overview
Nocturnal asthma is defined by a drop in forced expiratory volume in 1 second (FEV1) of at least 15% between bedtime and awakening in patients with clinical and physiologic evidence of asthma. The pathophysiology of nocturnal asthma is closely associated with the chronobiology and the science of biologic processes that have time-related rhythms. Hence, understanding the circadian rhythm is important to interpret the changes in pulmonary function that occurs in sleeping asthmatics. A large population based study reported dyspneic episodes without therapy in asthmatics occurred between 10 P.M. and 7 A.M. Another population based survey that assessed 7729 patients, reported approximate 74% patients woke-up at least once a week with symptoms, 64% woke-up three times per week, and 39% patients woke-up every night with symptoms.

# Epidemiology and Demographics
Nocturnal worsening of asthma is very common clinical finding in asthmatics affecting approximately 75% of asthmatics who awaken at least once per week because of symptoms, and approximately 40% experience nocturnal symptoms on a nightly basis.
Non-gonococcal urethritis

# Overview
Non-gonococcal urethritis (NGU) is an inflammation of the urethra which is not caused by gonorrheal infection.

# Symptoms
The symptoms of urethritis can include pain or a burning sensation upon urination (dysuria), a white/cloudy discharge and a feeling that one needs to pass urine frequently; however, there are often no symptoms.

# Causes
Urethritis can be caused by a number of organisms, including Neisseria gonorrheae, Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma genitalium, Trichomonas vaginalis, Herpes simplex virus, and Candida albicans, and by a number of non-infectious causes, including urethral stricture, foreign bodies, trauma, Reiter's syndrome, and various autoimmune and allergic conditions.
Of these many causes, the vast preponderance of cases are due to either gonorrhea or chlamydia. It is currently estimated that 50% of NGU cases are caused by chlamydia, with the remainder due to other causes.

# Diagnosis
Historically, it has been easy to test for the presence of gonorrhea by viewing a Gram's stain of the urethral discharge under a microscope: the causative organism is distinctive in appearance. Thus, one of the major causes of urethritis can be identified by a simple common test, and the distinction between gonococcal and non-gonococcal urethritis arose historically for this reason.
Identifying chlamydia, the other major cause of urethritis, has required more sophisticated technology, but is now more widely available.  These two tests combined identify the cause of most treatable forms of urethritis. If tests for gonorrhea and chlamydia are negative, and the cause of the urethritis has not been otherwise identified, the term non-specific urethritis (NSU) is used.  The terms "NGU" and "NSU" are sometimes used inconsistently, but these are the most common meanings in the modern era of treatment.

# Treatment
Treatment is based on the prescription and use of the proper antibiotics depending on the strain of the ureaplasma.
Because of its multi-causative nature, initial treatment strategies involve using a broad range antibiotic that is effective against chlamydia (such as doxycycline). It is imperative that both the patient and any sexual contacts are treated. Women who are infected with the organisms that cause NGU may develop pelvic inflammatory disease. If symptoms persist, follow-up with a urologist may be necessary to identify the cause.
If left untreated, complications include epididymitis and infertility. Consistent and correct use of latex condoms during sexual activity greatly reduces the likelihood of infection.
Non-parametric statistics

# Overview
Non-Parametric statistics are statistics where it is not assumed that the population fits any parametrized distributions.  Non-Parametric statistics are typically applied to populations that take on a ranked order (such as movie reviews receiving one to four stars).
The branch of statistics known as non-parametric statistics is concerned with non-parametric statistical models and non-parametric statistical tests.
Non-parametric models differ from parametric models in that the model structure is not specified a priori but is instead determined from data. The term nonparametric is not meant to imply that such models completely lack parameters but that the number and nature of the parameters are flexible and not fixed in advance. Nonparametric models are therefore also called distribution free or parameter-free.
- A histogram is a simple nonparametric estimate of a probability distribution
- Kernel density estimation provides better estimates of the density than histograms.
- Nonparametric regression and semiparametric regression methods have been developed based on kernels, splines, and wavelets.
Non-parametric (or distribution-free) inferential statistical methods are mathematical procedures for statistical hypothesis testing which, unlike parametric statistics, make no assumptions about the frequency distributions of the variables being assessed. The most frequently used tests include
- binomial test
- Anderson-Darling test
- chi-square test
- Cochran's Q
- Cohen's kappa
- Efron-Petrosian Test
- Fisher's exact test
- Friedman two-way analysis of variance by ranks
- Kendall's tau
- Kendall's W
- Kolmogorov-Smirnov test
- Kruskal-Wallis one-way analysis of variance by ranks
- Kuiper's test
- Mann-Whitney U or Wilcoxon rank sum test
- McNemar's test (a special case of the chi-squared test)
- median test
- Pitman's permutation test
- Siegel-Tukey test
- Spearman's rank correlation coefficient
- Student-Newman-Keuls (SNK) test
- Wald-Wolfowitz runs test
- Wilcoxon signed-rank test.
Nonparametric tests have less power than the appropriate parametric tests, but are more robust when the assumptions underlying the parametric test are not satisfied.
Northwest Biotherapeutics
Northwest Biotherapeutics is an American pharmaceutical company that focuses on developing immunotherapies against different types of cancer.

# Mission
NWBT's stated goals stress product quality and purity, innovation, and efficient production.

# Technology
The DCVax technology upon which NWBT's therapies rely involves injecting cancer patients with dendritic cells, which contain high levels of the same antigens found in tumor cells. The immune system, alerted by these antigens, attacks the cancer as well as the injected cells.

# Products
DCVax Brain, the first vaccine against brain cancer approved by the American Food and Drug Administration (FDA), is set to be distributed at select centers in Switzerland by September 2007. DCVax Prostate has also been approved by the FDA for trials.

# Footnotes and references
-  "First brain cancer vaccine approved in Switzerland". Yahoo! News. 2007-07-09. Retrieved 2007-07-09. Check date values in: |date= (help).mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
Obturator internus muscle

# Overview
The obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis.
It exits the pelvic cavity through the lesser sciatic foramen.
The Obturator internus is situated partly within the lesser pelvis, and partly at the back of the hip-joint.

# Origin and insertion
It arises from the inner surface of the antero-lateral wall of the pelvis, where it surrounds the greater part of the obturator foramen, being attached to the inferior rami of the pubis and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brim, reaching from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front.
It also arises from the pelvic surface of the obturator membrane except in the posterior part, from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve, and to a slight extent from the obturator fascia, which covers the muscle.
The fibers converge rapidly toward the lesser sciatic foramen, and end in four or five tendinous bands, which are found on the deep surface of the muscle; these bands are reflected at a right angle over the grooved surface of the ischium between its spine and tuberosity.

# Bursa/bands
This bony surface is covered by smooth cartilage, which is separated from the tendon by a bursa, and presents one or more ridges corresponding with the furrows between the tendinous bands.
These bands leave the pelvis through the lesser sciatic foramen and unite into a single flattened tendon, which passes horizontally across the capsule of the hip-joint, and, after receiving the attachments of the gemelli, is inserted into the forepart of the medial surface of the greater trochanter above the trochanteric fossa.
A bursa, narrow and elongated in form, is usually found between the tendon and the capsule of the hip-joint; it occasionally communicates with the bursa between the tendon and the ischium.

# Additional images
- Right hip bone. External surface.
- Right hip bone. Internal surface.
- Right femur. Anterior surface.
- Structures surrounding right hip-joint.
- Muscles of the gluteal and posterior femoral regions.
- Sacral plexus of the right side.
Olfactory receptor neuron

# Overview
An olfactory receptor neuron, also called an olfactory sensory neuron, is the primary transduction cell in the olfactory system.

# In vertebrates
Humans have about 40 million olfactory receptor neurons. In vertebrates, olfactory receptor neurons reside on the olfactory epithelium in the nasal cavity.  These cells are bipolar neurons with a dendrite facing the interior space of the nasal cavity and an axon that travels along the olfactory nerve to the olfactory bulb.

## Structure
Many tiny hair-like cilia protrude from the olfactory receptor cell's dendrite into the mucus covering the surface of the olfactory epithelium.  The surface of these cilia is covered with olfactory receptors, a type of G protein-coupled receptor. Each olfactory receptor cell expresses only one type of olfactory receptor, but many separate olfactory receptor cells express olfactory receptors which bind the same set of odors.  The axons of olfactory receptor cells which bind the same odors glomeruli in the olfactory bulb.

## Function
A given olfactory receptor can bind to a variety of odor molecules with varying affinities. The activated olfactory receptor in turn activates the intracellular G-protein GOLF (GNAL), and adenylate cyclase and production of Cyclic AMP opens ion channels in the cell membrane, resulting in an influx of sodium and calcium ions into the cell. This influx of positive ions causes the neuron to depolarize, generating an action potential.

## Regeneration
Individual olfactory receptor neurons are replaced approximately every 40 days by neural stem cells residing in the olfactory epithelium.  The regeneration of olfactory receptor cells, as one of the only few instances of adult neurogenesis in the central nervous system, has raised considerable interest in dissecting the pathways for neural development and differentiation in adult organisms.

# In insects
In insects, olfactory receptor neurons typically reside on the antenna. Much like in vertebrates, axons from the sensory neurons converge into glomeruli in the antennal lobe.