1. Diagnostic testing II

2. Previously…. • Guidelines for evaluating tests have been discussed • Population spectrum • Reference standard • Verification bias • Masking readers of the test and outcome • Review bias • Quantitate uncertainty • Confidence interval

3. Outline • Identifying potential tests • Creating groups • Evaluating the validity of the tests/groups

4. Identifying potential tests • Test refers to any independent variable / predictor: • Clinical, histological features • Immunohistochemical, biochemical, molecular tests, etc

5. Identifying potential tests • Literature • Chart review • Expert opinion

6. Examples

7. I. Identifying bacteremia or bacterial meningitis in febrile infants • Review charts on febrile infants: • Identify cases with confirmed bacteremia/bacterial meningitis • Identify those without these disorders • Identify variables that occurred significantly more frequently in cases • Interview physicians • Review the literature • Create a panel of promising tests

8. I. Identifying bacteremia or bacterial meningitis in febrile infants • Pantell RH et al. JAMA 2004;291:1203-12 • Prospective cohort from which “tests” identified and rule developed • Stepwise use of tests • Clinical appearance: moderately/very ill vs well or minimally ill • Age: <25d vs ≥25 days • Temperature: ≥38.6 vs <38.6/normal • Defined high risk febrile infant • at least moderately ill or <25d or To ≥38.6 • Training set • Next step: Evaluate this test panel in another cohort of febrile infants following diagnostic test methodology

9. II. Ottawa ankle rules Stiell IG, et al. JAMA 1994;271:827-32 • To develop decision rule to predict fractures in patients with ankle injuries, at same time decrease use of radiology • Set sensitivity to identify fractures at 100% • 32 clinical variables, based on clinical experience and previous studies • Applied the 32 variables prospectively in 750 patients • Final rule had 4 variables; applied simultaneously; rule considered positive if any test positive • Shown prospectively in numerous settings to have high sensitivity for ankle fracture while reducing number of radiographs

10. III. Distinguishing between serous and endometrioid endometrial carcinomaOnuma K et al. • Serous carcinoma requires staging, chemo • Can sometimes be difficult to tell apart • Clinical variables: age, BMI, stage, HRT • Any helpful? • 5 IHC markers: p16, p53, B-catenin, ER, PR • Did any provide additional information once clinical variables taken into account?

11. Searched pathology database for hysterectomies diagnosed as serous / endometrioid • 46 confirmed endometrioid and 35 confirmed serous by 2 independent observers • Uncertain cases excluded*

12. Training set • Univariate analysis of each variable against histologic type • Multivariate analysis • Incremental contribution of each variable • Final model of 4 independent variable • P16, p53, PR, ER

13. Problem • We don’t need markers for histologically unequivocal cases • Really want to know if these markers are useful in equivocal cases

14. Problem • Febrile infant and ankle studies, rule created in • infants known to be culture + or – • in patients with X-ray confirmed fracture or no fracture • Can evaluate the rule in unknown population (febrile infants / patients with ankle injury) and compare to gold standard of culture / X-ray • In equivocal serous / endometrioid cancers (the unknown population), what is the gold standard? • Consensus histology diagnosis? • Survival?

15. Creating groups

16. Colorectal carcinoma:Identifying prognostic groupsFurlan D, et al. Modern Pathol 2011;24:126-37 • Purpose: create morphomolecular classification for colorectal cancer • 13 routine clinicopathologic features • 5 molecular markers • Cluster analysis

17. Cluster A • Right colon, special type (mucinous, medullary, papillary, cribriform), higher grade, microsattelite instability, low stage • Cluster B • Common type, left colon, LVSI, loss of heterozygosity, high stage • Cluster C • Special types, non LVSI, low stage, MGMT methylation

18. Are these clusters useful? • Survival information (but given by stage) • Perhaps allow targeted therapy

19. Summary • Methods to identify tests, create groups • This is preliminary information • Must be evaluated in patients with proper test methodology before information is ready for clinical use