Negative predictive value

Plasmin cleaves fibrin at different positions. Of high clinically practical relevance is the cleavage of the fibrin y-chain that results in D-Dimers (Fig. 11). D-Dimers are specific for fibrin cleavage by plasmin. They can easily be detected by commercially available assays and are used to exclude thrombosis. A negative test for D-Dimer has a high negative predictive value for a thrombosis. 

Vernassiere C, Trechot P. Commun N. et al Low negative predictive value of skin tests in investigating delayed reactions to radiocontrast media. Contact Dermatitis 2004 50 359-366. 

Histamine concentrations are maximal almost immediately, decrease thereafter with a half-life of about 20 min, and should be assayed within the first hour of a reaction. The sensitivity of this test for the diagnosis of anaphylaxis was estimated at 75%, the specificity at 51%, the positive predictive value at 75% and the negative predictive value at 51%. Tryptase reaches a peak in the patient s serum 30 min after the first clinical manifestations. Its half-life is 90 min, and the levels usually decrease over time. In a recent series, the sensitivity was estimated at 64%, specificity at 89.3%, positive predictive value at 92-95%, and negative predictive value at 54.3% [9]. 

Biomarkers of sepsis have been controversial. The routine use of endotoxin, procalcitonin, or other markers is not routinely recommend. Concentrations of procalcitonin in serum are usually increased in sepsis, but fail to differentiate between infection and inflammation. However, procalcitonin has a high negative predictive value and could allow for the discontinuation of antibiotics. 

The authors also evaluated the performance of various DES-T and DES cutoffs for detecting taxon members defined by Bayesian probabilities. Waller and Ross found that DES-T cutoffs work much better than the cutoffs on the DES because they have higher sensitivity, specificity, and positive and negative predictive values. One could say that the authors stacked the deck in favor of the DES-T, as the Bayesian probabilities and DES-T scores are based on the same data. However, this redundancy is unavoidable, since there is no other method of assessing taxon membership. It is important to evaluate the qualities of DES-T cutoffs for studies that will use the DES-T, rather than the Bayesian scoring scheme. 

B. Strength of Effect Positive and Negative Predictive Values of Pharmacogenetic Tests5... 

In the discussion that follows positive predictive value (PPV) is defined as the proportion of people with a positive test result who have or will develop an unwanted response when the drug is administered. Negative predictive value (NPV) is the proportion of people with a negative test who will not have or develop an unwanted response when the drug is administered. 

The value of PET for predicting contractile function after revascularization depends on whether perfusion or metabolic imaging is performed, or both. For perfusion imaging alone, if regional blood flow is preserved to more than 50% of normal, contractile dysfunction will likely recover with an average positive and negative predictive value of 63% (range... 

NPV = negative predictive value PPV = positive predictive value ACS = acute coronary syndrome PTCA = percutaneous transluminal coronary angioplasty PCI = percutaneous coronary intervention DCCV = direct-current cardioversion A fib = atrial fibrillation NA = not applicable. 

The negative predictive value means that the test result is negative and the patient does not have food allergy (Chapman et al., 2006). 

A negative prick test usually rules out food allergy mediated by IgE mechanisms. The PST with a commercial food allergen extract has a high negative predictive value (>95%), whereas a positive PST has only a 30%-40% positive predictive value (Burks and Sampson, 1992 Sampson, 1999a Nowak-Wegrzyn and Sampson,... 

A negative test (specific IgE) <0.35kJ/L has a high negative predictive value (>95%) (Nowak-Wegrzyn and Sampson, 2006). 

Providing adequate diagnostic accuracy, that is diagnostic sensitivity and diagnostic specificity, determined by the desired positive and negative predictive values which depend on disease frequency [124]. 

For understanding sensitivity, specificity, false negative predictive value, and false positive predictive value, consider the four cells and two column margins of Table 2, where individuals are cross-classified with respect to their true sero-status versus observed sero-status. Sensitivity is represented by Se = / (testing outcome + truth is +) and specificity is Sp = / (testing outcome - truth is -). With these definitions and with p denoting the probability of an individual having... 

The next issue of evaluation mechanism is to define a measure for the quality of a particular prediction. For sequence discrimination problem, which involves a yes or no answer (e.g., binding or non-binding, member or non-member), the performance can be measured by sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and correlation coefficient, as shown in... 

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