A General Latent Class Model for Performance Evaluation of Diagnostic Tests in the Absence of a Gold Standard: An Application to Chagas Disease

Table 5

Summary of the posterior probability estimates obtained for the parameters that measure the effect of the cth covariate on the sensitivity and specificity of kth test and on disease prevalence in vth stratum, using model ModII (𝐿=6,𝑀=3,𝑉=2).

Sensitivity (𝛼𝑐𝑘)					Specificity (𝛽𝑐𝑘)
Test	Parameter	Mean	P2.5%	P97.5%	Test	Parameter	Mean	P2.5%	P97.5%
ELISA	𝛼11	5.91	3.03	8.79	ELISA	𝛼01	3.47	1.80	5.10
	𝛾111	0.50	0.02	0.96		𝛾011	−1.92	−2.79	−0.94
	𝛾112	0.51	0.03	1.00		𝛾012	−2.10	−2.90	−1.14
	𝛾113	0.50	−0.01	0.96		𝛾013	−2.12	−2.89	−1.11
IIF	𝛼12	5.79	2.89	8.82	IIF	𝛼02	6.51	3.01	9.73
	𝛾121	0.51	0.04	0.99		𝛾021	−2.08	−2.89	−1.02
	𝛾122	0.49	0.00	0.98		𝛾022	−2.12	−2.89	−1.16
	𝛾123	0.50	0.02	1.00		𝛾023	−2.12	−2.89	−1.10
IHA	𝛼13	5.77	2.76	8.65	IHA	𝛼03	6.56	2.88	10.01
	𝛾131	0.51	0.03	0.99		𝛾031	−2.10	−2.86	−1.05
	𝛾132	0.49	0.01	0.97		𝛾032	−2.11	−2.91	−1.11
	𝛾133	0.51	0.04	0.98		𝛾033	−2.12	−2.85	−1.15
HEMO	𝛼14	−0.50	−0.78	−0.22	HEMO	𝛼04	100	100	100
	𝛾141	0.38	−0.06	0.84		𝛾041	0	0	0
	𝛾142	0.45	0.02	0.89		𝛾042	0	0	0
	𝛾143	0.31	−0.12	0.74		𝛾043	0	0	0
c-ELISA	𝛼15	5.76	2.87	8.75	c-ELISA	𝛼05	2.00	1.01	2.97
	𝛾151	0.51	0.02	1.00		𝛾051	−1.91	−2.77	−0.94
	𝛾152	0.49	0.04	0.97		𝛾052	−2.11	−2.90	−1.07
	𝛾153	0.49	0.00	0.98		𝛾053	−2.08	−2.85	−1.11
rec-ELISA	𝛼16	5.72	2.82	8.70	rec-ELISA	𝛼06	6.50	3.16	10.03
	𝛾161	0.21	−0.18	0.74		𝛾061	−2.08	−2.87	−1.05
	𝛾162	0.54	0.07	1.00		𝛾062	−2.09	−2.90	−1.03
	𝛾163	0.46	−0.05	0.97		𝛾063	−2.11	−2.88	−1.09
Prevalence (𝛾𝑐𝑣)
Stratum	Parameter	Mean	P2.5%	P97.5%	Stratum	Parameter	Mean	P2.5%	P97.5%
I	𝛼1	0.50	0.21	0.81	II	𝛼2	−2.01	−2.92	−1.03
	𝛾11	0.51	0.11	0.91		𝛾21	0.41	−0.04	0.84
	𝛾12	0.43	0.00	0.85		𝛾22	0.49	0.03	0.94
	𝛾13	0.69	0.28	1.12		𝛾23	0.43	−0.02	0.89

P2.5%: 2.5th percentile; P97.5%: 97.5th percentile; ELISA: enzyme-linked immunosorbent assay; IIF: indirect immunofluorescence; IHA: indirect hemagglutination; HEMO: blood culture; c-ELISA: conventional ELISA using the Biomanguinhos kit; rec-ELISA (recombinant ELISA using the Biomanguinhos kit and CRA and FRA antigens); 𝑐=1: AGE-age (≤30, >30 years); 𝑐=2: GEN-gender (male, female); 𝑐=3: RFE-presence of at least two of three risk factors epidemiological (origin from an endemic region, contact with the vector transmitting the disease, and family history of Chagas’ disease); Stratum I (𝑣=1) donors with negative or positive serology and Stratum II (𝑣=2) with inconclusive serology in the screening test; 𝛾_1𝑘𝑐: effect of the cth covariate on the sensitivity of kth test; 𝛾_0𝑘𝑐: effect of the cth covariate on the specificity of kth test; 𝛾_𝑣𝑐: effect of the cth covariate on disease prevalence in vth stratum.