Table 1.

Sensitivity and positive predictive value (PPV) of various algorithms for confirming psoriasis (PsO) and psoriatic arthritis (PsA). Kaiser Permanente Autoimmune Disease Registry, Northern California, 1996–2009.^*

Disease codes and rendering physician	Chart Review**
	Number in the population	Number reviewed*	No. of true positives	No. of false positives	Sensitivity (95% CI)	PPV (95% CI)	Estimated no. of true positives in the population
PsO without PsA
≥ 1 Any Physician	83,701	87	65	22	100***	78
≥ 1 Dermatology	59,671	66	59	7	91 (80–96)	89 (79– 95)	53,342
≥ 2 Dermatology	39,835	43	41	2	63	95
≥ 1 Non-Dermatology	24,022	21	6	15	9	29
PsA without PsO
≥ 1 Any physician	1,061	107	57	50	100***	53
≥ 1 Rheumatology	790	73	49	24	86	67
≥ 2 Rheumatology	605	54	44	10	77 (64–87)	81 (68–90)	493
≥ 1 Non-Rheumatology	271	34	8	26	14	24
PsO with PsA
≥ 1 Any physician	4,126	50	32	18	100***	64 (49–77)
≥ 1 Dermatology AND ≥1 Rheumatology	3,427	35	25	10	78 (60–90)	71 (53–85)	2,448
Using the best performing algorithms****
PsO with or without PsA	63,098	101	91	10	88 (89–93)	90 (83–95)	55,790
PsA with or without PsO	4,032	89	71	18	73 (63–82)	80 (70–88)	2,941

^*The best performing algorithms are presented in bold.

^**A random sample of approximately 0.1% of patients with psoriasis codes alone, 1% of patients with psoriasis and psoriatic arthritis codes, and 10% of patients with psoriatic arthritis codes alone was selected, by assigning random numbers from 0–1.000 and selecting all cases with numbers below 0.001, 0.010, and 0.10, respectively, for validation by chart review.

^***By definition.

^****For PsO, ≥1 PsO diagnosis from dermatology. For PsA, ≥2 PsA diagnosis from rheumatology or ≥1 PsA diagnosis from rheumatology AND ≥1 PsO diagnosis from dermatology.