The Student Room Group

True pos/neg HELP PLEASEE!!!!

Hi, I am trying to work out the true positive/negative/false pos/neg values from this data for both CTA scans and VQ scans, and am very confused!!!

100 patients selected for examination. 23 patients were clinically diagnosed with pulmonary embolism. 14 patients had CTA positive for PE, and 55 had negative CTA for PE. 31 out of 100 CTAs were non-diagnostic. The sensitivity and specificity of the two diagnostic modalities were similar, sensitivity for CTA and spect V/Q scan were 67% and 72%, respectively. Specificity of CTA and spect V/Q were 96% and 94%, respectively. Interestingly, only 9 patients had an indeterminate spect V/Q scans, of which only 1 was diagnosed with PE. CTA showed a lower false positive rate (2.6%) compared to V/Q scans (5.2 %).

I think for CTA: TP = 14, TN = 55, FP = 5.2, FN = 9????
for VQ scans: TP = ?, TN = ??????

PLease someone, help me sort this out in my head! Having a nightmare!!

Thank youuuuu :biggrin:
Reply 1
Original post by veryconfusedhelp
Hi, I am trying to work out the true positive/negative/false pos/neg values from this data for both CTA scans and VQ scans, and am very confused!!!

100 patients selected for examination. 23 patients were clinically diagnosed with pulmonary embolism. 14 patients had CTA positive for PE, and 55 had negative CTA for PE. 31 out of 100 CTAs were non-diagnostic. The sensitivity and specificity of the two diagnostic modalities were similar, sensitivity for CTA and spect V/Q scan were 67% and 72%, respectively. Specificity of CTA and spect V/Q were 96% and 94%, respectively. Interestingly, only 9 patients had an indeterminate spect V/Q scans, of which only 1 was diagnosed with PE. CTA showed a lower false positive rate (2.6%) compared to V/Q scans (5.2 %).

I think for CTA: TP = 14, TN = 55, FP = 5.2, FN = 9????
for VQ scans: TP = ?, TN = ??????

PLease someone, help me sort this out in my head! Having a nightmare!!

Thank youuuuu :biggrin:



I suspect the problem is no more than GCE level, but the context, at least for me, is very scary as they are some thing which need further defining or clearing.

My advice is
Post a photo of the question.
Put a carbon copy in the "medical and related disciplines" section of the undergrads.

Truly sorry I cannot be more helpful

Quick Reply