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Good Positive and Negative Likelihood Ratios

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Pneumocystis jirovecii Pneumonia: Likelihood Ratios

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Prevalence

Population / Calculator	Prevalence	Comments / Study / Link
HIV, CD4 count 200-350	0.5%	[From UpToDate] One study showed that the incidence of PCP with a CD4 count of 201 to 350 cells/mm3 was 0.5 percent.
HIV, CD4 count < 200	8%	[From UpToDate] Within six months of the CD4 count falling below 200 cells/mm3, 8 percent of patients developed PCP.
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The likelihood ratios of findings for Pneumocystis jirovecii Pneumonia are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Good Positive and Negative Likelihood Ratios
Finding	Result	+LR	-LR
[ + ] High-Resolution Chest CT (HRCT)	+ 0 -	9.1	0
May be useful for ruling out PCP Study: http://www.ajronline.org/cgi/reprint/162/3/547 Diagnosis of thoracic complications in AIDS: accuracy of CT. Hartman TE; Primack SL; Muller NL; Staples CA AJR Am J Roentgenol 1994 Mar;162(3):547-53.
[ + ] bronchoalveolar lavage (BAL)	+ 0 -	inf	0.2
Sensitivity can be increased to 98 if BAL is site-directed by chest imaging. Study: http://www.ncbi.nlm.nih.gov/sites/entrez Aerosolized pentamidine: effect on diagnosis and presentation of Pneumocystis carinii pneumonia. Jules-Elysee KM; Stover DE; Zaman MB; Bernard EM; White DA Ann Intern Med 1990 May 15;112(10):750-7.
[ + ] Respiratory specimens from sputum induction	+ 0 -	inf	0.5
Specificity found to be in 55-92% range in meta-analysis below. Using an immunofluorescent staining technique to evaluate sputum specimens induced by the inhalation of hypertonic saline. Study: http://erj.ersjournals.com/cgi/content/full/20/4/982 Meta-analysis of diagnostic procedures for Pneumocystis carinii pneumonia in HIV-1-infected patients. Cruciani M; Marcati P; Malena M; Bosco O; Serpelloni G; Mengoli C Eur Respir J 2002 Oct;20(4):982-9.

Findings With Unspecified Accuracy
Finding	Result	+LR	-LR
[ + ] Diffusing capacity for carbon monoxide (DLCO)		No accuracy specified.
PCP is highly unlikely if the DLCO is normal, defined by 70 percent of the predicted value or greater Study: http://www.chestjournal.org/cgi/content/full/115/4/1025 Performance of an algorithm to detect Pneumocystis carinii pneumonia in symptomatic HIV-infected persons. Pulmonary Complications of HIV Infection Study Group. Huang L; Stansell J; Osmond D; Turner J; Shafer KP; Fulkerson W; Kvale P; Wallace J; Rosen M; Glassroth J; Reichman L; Hopewell P Chest 1999 Apr;115(4):1025-32.
[ + ] O2 desaturation with exercise		No accuracy specified.
Assessment of oxygenation at rest and with exercise. The presence of PCP is highly unlikely if the response to exercise is normal, ie, a decrease in the alveolar-arterial oxygen gradient or an increase in the oxygen saturation with exercise. Study: http://www.ncbi.nlm.nih.gov/pubmed/3044683 Pulmonary function tests. Stover DE; Meduri GU Clin Chest Med 1988 Sep;9(3):473-9.
[ + ] High LDH		No accuracy specified.
An LDH of <220 IU/L rules out PCP in an immunocompromised patient Study: no study specified.
[ + ] Low CD4 count		No accuracy specified.
Study: no study specified.