A Screening Program Uses A Home Testing Urine Kit To Detect

A Screeningprogram Uses A Home Testing Urine Kit To Detect Disease X

A screening program uses a home testing urine kit to detect disease X. You decide to test the kit in your community of 1,000 adults. You know that the prevalence of disease X in your community is 20%, meaning that 200 individuals have the disease at any given point in time. The test correctly identified 150 individuals with the disease while it was able to correctly identify 700 individuals without the disease.

Your task is to draw a 2x2 contingency table based on these data. Then, you will calculate the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the test. Finally, provide a 1- to 2-paragraph interpretation of your results, explaining what they suggest about the effectiveness of the urine testing kit in this community. Your paper should be properly cited, well-organized, and free of spelling and grammatical errors, covering approximately 1-2 pages.

Paper For Above instruction

The evaluation of diagnostic tests, such as the urine kit for disease X, involves understanding measures like sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). These metrics give a comprehensive picture of a test's accuracy and utility in screening populations, especially when the prevalence of the disease is known. Based on the provided data, the calculation of these measures begins with constructing a 2x2 contingency table.

Constructing the 2x2 table:

The total population tested is 1,000 adults, with a disease prevalence of 20%. Therefore, the number of individuals with disease X is 200, and those without the disease are 800. The data indicates that the test correctly identified 150 infected individuals, which are true positives (TP). It also correctly identified 700 healthy individuals, which are true negatives (TN). To complete the table, we determine the false negatives (FN) and false positives (FP). Since 150 out of 200 actual cases were correctly identified, the remaining 50 were missed (FN). Conversely, as 700 out of 800 healthy individuals were correctly identified, 100 were incorrectly identified as diseased (FP).

| | Disease Present | Disease Absent | Total |

|-------------------------|------------------|----------------|-------------|

| Test Positive | 150 (TP) | 100 (FP) | 250 |

| Test Negative | 50 (FN) | 700 (TN) | 750 |

| Total | 200 | 800 | 1,000 |

Calculations:

- Sensitivity measures the proportion of actual positives correctly identified:

\[

\text{Sensitivity} = \frac{\text{TP}}{\text{TP} + \text{FN}} = \frac{150}{150 + 50} = \frac{150}{200} = 0.75 \text{ or } 75\%

\]

- Specificity measures the proportion of actual negatives correctly identified:

\[

\text{Specificity} = \frac{\text{TN}}{\text{TN} + \text{FP}} = \frac{700}{700 + 100} = \frac{700}{800} = 0.875 \text{ or } 87.5\%

\]

- Positive Predictive Value (PPV) indicates the probability that a person with a positive test truly has the disease:

\[

\text{PPV} = \frac{\text{TP}}{\text{TP} + \text{FP}} = \frac{150}{150 + 100} = \frac{150}{250} = 0.6 \text{ or } 60\%

\]

- Negative Predictive Value (NPV) reflects the probability that a person with a negative test does not have the disease:

\[

\text{NPV} = \frac{\text{TN}}{\text{TN} + \text{FN}} = \frac{700}{700 + 50} = \frac{700}{750} \approx 0.933 \text{ or } 93.3\%

\]

Interpretation:

The urine testing kit exhibits a sensitivity of 75%, meaning it correctly identifies three-fourths of those with disease X. This level suggests the kit is reasonably effective at detecting true positive cases but does miss about 25% of actual cases, which highlights a limitation in disease detection. The specificity of 87.5% indicates it effectively identifies healthy individuals, reducing false positives. The PPV of 60% signifies that when the test indicates disease, there is a 60% chance the individual actually has the disease; thus, false-positive results are relatively common. Conversely, the high NPV of over 93% suggests that negative test results are reliably indicating the absence of disease, which is crucial in screening contexts to reassure the majority of healthy individuals.

Overall, these metrics suggest the urine testing kit is a useful screening tool, particularly valued for its high NPV, meaning it effectively rules out disease in most negative cases. However, the moderate PPV indicates confirmatory testing remains essential to avoid misdiagnosis based on false positives. When implementing such screening programs, these performance characteristics help determine the test's role—mainly to identify individuals needing further diagnostic evaluation while balancing the risks of false results. Further research could focus on improving sensitivity and PPV to enhance the test's overall diagnostic accuracy.

References

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