Detection criteria

The risk assessment process can be conducted by examining record types to see if they are GxP or non-GxP, and then applying severity checks, likelihood, and probability of detection criteria, as illustrated in Figure 15.2. The most severe scenarios shonld be linked to direct patient/consnmer impact. GxP noncompliance and broken license conditions are severe in their own right bnt not as critical as patient/consumer health in this analysis." Its likelihood will be influenced by the degree of human error in how the record is input and used. The probability of detection needs to take into account the probability of the impacted record being used. Once failure modes are understood, then the appropriate design controls can be introduced. These should be documented and validated as part of the computer system life cycle discussed earher in this book. 

Paramount in the study design is to ensure that sufficient numbers of samplers and/or exposure times are used to meet the goals of the study. Knowledge of how much chemical needs to be sampled to meet the detection criteria of the chemical analysis or toxicity tests will influence the study design. The number of samplers needed to satisfy the study requirements can be estimated using the following equation ... 

Table 3. d-spacing (A) of the missing non-overlapping standard reflection lines for the Bi-Mo-O and Bi-Mo-O-P phases satisfying the detection criteria (see text). 

ND = not detected. Criteria are no discernable radioactive peak, <0.01% radioactivity and not... 

The development of detection criteria always results from program requirements initiated by some general management guideline. In... 

Depending on the requirements and costs, one method may be chosen over another provided it registers sufficient reliability. For example, whereas visual inspection is unreliable for small defects compared to an instrument inspection, in some aerospace in-service applications, it can be more cost-effective or practical to use visual inspection on a frequent basis than to conduct a more sensitive and costly instrument inspection less frequently to achieve the same service reliability of a component. It is common to specify that inspections require a signal-to-noise ratio (SNR) of >2.5 for the system sensitivity to the detection criteria of designated features in a calibration standard. Under a normal curve distribution, this would provide better than 98.7% detectability. 

Although rate is the primary method that ICDs use to detect malignant ventricular arrhythmias, other arrhythmias, such as atrial fibrillation, atrial flutter, or sinus tachycardia may be associated with ventricular rates that would fall within the rate-detection criteria. Manufacturers have developed additional... 

Supraventricular tachycardia 35 5 Program additional detection criteria (sudden onset, morphology) Consider therapy for supraventricular arrhythmias (tachycardia, drugs, or AV node ablation for atrial fibrillation) Consider implantation of an atrial lead. 

Inappropriate therapy can occur in two instances supraventricular tachycardia that meets the detection criteria for ventricular tachyarrhythmia and false detection in the absence of arrhythmia. 

Almost any type of supraventricular tachycardia (atrial fibrillation, atrial flatter, atrial tachycardia, sinus tachycardia) may be associated with a ventricular rate that falls within the detection criteria for an ICD. In one stndy, approximately 70% of inappropriate therapies are due to supraventricular arrhythmias being misclassified as ventricular arrhythmias requiring therapy (81). 

Asymptomatic therapy, or ineffective therapy (antitachycardia pacing) Unknown Consider reprogramming the detection criteria to more rapidly provide therapy for ventricular arrhythmias. Evaluate effectiveness of antitachycardia pacing electrograms or via NIPS... 

Two scoring tables are given here for severity ranking Table 7 lists five possible scoring levels and relates to the effect a failure may have on customer relations Table 8 pertains to environmental, safety, and health levels and contains four possible scoring levels. Note that these tables enumerate abbreviated versions of the severity criteria, and that/or most of the scoring levels for the Severity, Occurrence and Detection criteria, two scoring possibilities are available for each narrative description. 

Detection Criteria, Limit of Detection, Limit of Determination... 

Depending whether the analytical method requires a calibration or not, one distinguishes between two different procedures for determining the detection criteria and the limit of detection. Because ion chromatography is an analytical method requiring calibration, both parameters can be derived from the calibration data. When employing analytical methods that cannot be calibrated, the detection criteria are determined via repeated analyses of blank samples. 

Funk et al. define the detection criteria [27,36] as the measuring value, for which the /i-error - with given cr-error of 5% - is just 50% (see Figure 9.8). In the terminology of error probability this means ... 

If based on the detection criteria the blank value is regarded to be exceeded, an error probability of only a = 5% is against it. However, with repeated analyses of this sample, 50% of all results will be below (J) = 50%), that is, the probability of not detecting this compound is 50%. 

For the practical determination of the detection criteria, the standard deviation Syo of the blank value Jq or the standard deviation of the intercept a of the linear calibration function is used, where the standard deviation should be calculated from at least = 6 measuring values. The detection criteria is then regarded as the upper limit of the blank value scatter... 

The term limit of detection XN [37,38] is defined as the smallest detectable amount of a compound. A quantitative analysis with reported concentrations is possible only when the analytical result is equal or larger than the limit of detection, because the required significance level is achieved only for such an analytical result [39] (see Figure 9.9). In contrast to the detection criteria, the limit of detection is a quantitative statement of the amount of substance. 

The numerical value for the limit of detection XN, like that of the detection criteria Lc, depends on the chosen significance levels and the degrees of freedom. 

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