Utility of the Rose Bengal Test as a Point-of-Care Test for Human Brucellosis in Endemic African Settings: A Systematic Review

Table 1

Summary of published studies that investigated the performance of Rose Bengal test compared to culture as the reference test for diagnosis of human Brucella spp. infection.

Study	Diagnostic tests investigated	RBT DSe and DSp reported	Patient groups used to assess RBT performance	Diagnostic criteria used to select patient groups	“True positive” or “true negative” patient group used	Country
Diaz et al. [2]	RBT, titrated RBT, SAT, Brucellacapt, Coombs, LFiC-IgM and IgG, culture.	No, but DSe and DSp can be calculated from values provided.	(1) Individuals with brucellosis confirmed by culture (n = 208), included a subset of patients broadly categorised as acute and chronic based on IgM and IgG profile determined by LFiC.	Clinical findings, laboratory criteria (culture, serology).	Suitable “true positive” patient group used. Based on culture-positive results and clinical and/or epidemiological criteria.	Spain
			(2) Individuals with professional contact with infected animals or products or accidentally injected with Brucella vaccine, but asymptomatic (n = 20).	Clinical findings, laboratory and epidemiological criteria.	NA
			(3) Brucellosis patients showing prozone effect (n = 11).
			(4) Patients with no brucellosis symptoms (serum sent to the lab for diagnosis of other infections) (n = 1559).	Clinical findings.	Suitable “true negative” patient group used. Even though patients had no brucellosis symptoms, no culture results were reported. Diagnosis based only on clinical and/or epidemiological criteria.
Gomez et al. [23]	Titrated RBT, MAT, Brucellacapt, ELISA IgG, IgM and IgA, culture	Yes, but patient group used to calculate DSp was unsuitable.	(1) Patients with acute brucellosis (n = 25).	Clinical findings and either positive culture or serology results (SAT ≥ 160).	Suitable “true positive” patient group used. Based on positive culture results and clinical findings.	Spain
			(2) Healthy individuals (blood donors) (n = 90).	Clinical findings (blood donors) and serology results.	Suitable “true negative” patient group used. Even though patients were considered “healthy,” culture was not performed. Diagnosis was based only on clinical findings and serology.
Mizanbayeva et al. [28]	RBT, SAT, LFA IgM and IgG, culture.	Yes, DSe reported, but DSp was not assessed.	Patients with clinical suspicion of brucellosis (n = 471). Patients divided into 3 categories: acute disease (<6 months of illness, n = 396), subacute (6–12 months of illness, n = 30), and chronic (>1 year of illness, n = 43). Culture performed on a subset of 76 patients, and 63/76 were culture-positive.	Clinical findings, laboratory findings (culture, serology).	Suitable “true positive” patient group used. Based on culture-positive results, clinical and/or epidemiological criteria.	Kazakhstan
					No “true negative” patient group assessed.
Ruiz-Mesa et al. [15]	RBT, culture	Yes, DSp can be calculated from values provided, but DSe for culture-positive patients could not be calculated.	(1) Individuals with brucellosis confirmed with culture (n = 711). A subset of patients with positive culture results (n = 445).	Laboratory (culture or serology) and clinical criteria.	Suitable “true positive” patient group used. Based on positive culture results and clinical findings.	Spain
			(2) Patients with different infectious, autoimmune, or neoplastic processes with a precise aetiological diagnosis, but which involved an initial differential diagnosis with brucellosis (n = 176). This was considered by authors as one of three control groups	Clinical criteria, serology done but not specified if done for this group.	Suitable “true negative” patient group used. Even though patients were not diagnosed with brucellosis, culture was not performed.
			(3) Individuals exposed repeatedly to Brucella spp. during work (n = 68). Considered one of three control groups.	Clinical and epidemiological criteria, serology done but not specified if done for this group.	NA. Culture was not performed, and patient group was exposed to brucellosis.
			(4) Asymptomatic patients with history of brucellosis who had received appropriate treatment and shown no evidence of relapse after 1 year (n = 26). Considered one of three control groups.	History, clinical, and epidemiological criteria, serology done but not specified if done for this group.	NA. Culture was not performed, and patient group had a history of brucellosis.
Saz et al. [30]	RBT, ELISA, SAT, Coombs, culture.	No, but DSe and DSp can be calculated from values provided.	(1) Patients from whom Brucella melitensis was isolated (n = 208).	Laboratory criteria (culture and serology).	Suitable “true positive” patient group used. Based on positive culture results and clinical findings.	Spain
			(2) Patients with suspected brucellosis and positive results by ≥two conventional tests (n = 177).	Clinical findings and laboratory criteria (serology—positive RBT, SAT ≥ 80 and ≥160, Coombs).	NA. Culture was not performed.
			(3) Patients with fever but no other symptoms of brucellosis, from whom no Brucella spp. were isolated and for whom all conventional tests were negative (n = 107).	Based on clinical findings, negative culture and serology results (ELISA).	Suitable “true negative” group used. Based on negative culture results, serology and clinical findings.
Serra and Vinas [19]	RBT, SAT, Coombs, ELISA IgG and IgM, CFT, culture.	Yes, DSe of the “true positive” group could be calculated independently, but DSp of the “true negative” group could not be calculated based on the information provided.	(1) Patients with primary infection (no personal history of brucellosis) and showing acute clinical symptoms (n = 38).	Based on either (1) positive culture and serology results (SAT ≥ 160) and clinical evidence, or (2) clinical evidence and positive serology (Coombs test).	Suitable “true positive” group used. Based on positive culture results and clinical criteria.	Spain
			(2) Individuals living in the same area examined (n = 346). This group was considered a “negative-healthy” population and used as a control group and compared with the above group (patients with primary infection).	No information provided on laboratory or epidemiological criteria.	Suitable “true negative” patient group used. Even though patients were considered “healthy,” culture results were not reported. Based on clinical findings only.
			(3) Patients with evidence of previous infection (n = 24) based on (i) brucellosis being diagnosed previously or (ii) epidemiological data compatible with long exposure (such as in farmers and veterinarians) and an immune response of “secondary type” (IgG predominating).	Based on positive culture and serology results, clinical and epidemiological criteria.	NA. Patients with a history of brucellosis infection, and culture was performed.
			(4) Healthy individuals in whom brucellosis had previously been diagnosed and subsequently treated more than 2 years before, with no subsequent symptoms of the disease (“cured” population) (n = 55). This group was used as a control group and compared with the above group (patients with evidence of previous infection).	Based on clinical and epidemiological criteria.	Not suitable “true negative” group. Culture was not performed, and individuals had a history of brucellosis.
Sisirak and Hukić [20]	RBT, ELISA IgM and IgG, culture.	Yes, but DSp could not be calculated independently.	Patients with signs of brucellosis at presentation (n = 91). Though not clearly presented, patients were divided into stages of illness based on the duration of illness.	Laboratory criteria (culture and/or serology), clinical findings.	Suitable “true positive” group. Based on positive culture results and clinical criteria.	Bosnia and Herzegovina
					Not suitable “true negative” group used. Unclear information provided on culture and RBT results.
Taleski [21]	RBT, Coombs, 2-ME, CFT, Indirect ELISA, cELISA, FPA, PCR, culture.	No, DSe and DSp were not reported and could not be calculated independently.	(1) Patients with acute brucellosis (n = 592). Diagnosis based on epidemiological data, clinical findings, and laboratory tests.	Epidemiological data, clinical findings, and laboratory tests.	Not suitable “true positive” group. No information provided on culture and RBT results for the group.	Macedonia
			(2) Healthy, voluntary blood donors (n = 100). Diagnosis based on epidemiological data, clinical findings, and laboratory tests.	Epidemiological data, clinical findings, and laboratory tests.	Not suitable “true negative” group. No information provided on culture and RBT results for the group.
			(3) Healthy people from endemic areas (n = 69). Diagnosis based on epidemiological data, clinical findings, and laboratory tests.	Epidemiological data, clinical findings, and laboratory tests.	Not suitable “true negative” group. No information provided on culture and RBT results for the group.
Yumuk et al. [31]	RBT, culture.	No, information provided is incomplete to allow for independent calculation of DSe and DSp.	Patients with clinical signs of brucellosis at presentation. Enrolled if Brucella spp. positive on culture. Patients divided into two groups: (1) antinuclear antibody- (ANA-) positive group (n = 211); 209 patients with autoimmune, infectious, or neoplastic condition and differential diagnosis of brucellosis and 2 patients with brucellosis and (2) ANA-negative group (n = 70); 30 patients with brucellosis but with differential diagnosis of autoimmune disease and 40 healthy individuals.	Clinical findings and laboratory criteria (culture).	Not suitable “true positive” group. Information provided on culture, and RBT results are unclear.	Turkey
					Not suitable “true negative” group. Information provided on culture, and RBT results are not clear.
Mert et al. [32]	RBT, STAT, culture	No, information provided is incomplete to allow for independent calculation of DSe and DSp.	(1) Patients with culture-positive brucellosis (n = 30).	Clinical findings, laboratory criteria (culture, serology).	Suitable “true positive” patient group. Culture performed, but incomplete information provided on culture and RBT results.	Turkey
			(2) Patients with diseases that mimic brucellosis clinically (military tuberculosis, malaria, typhoid fever, adult-onset Still’s disease, systemic lupus erythematosus, rheumatoid arthritis, sarcoidosis, and active lymphoma) (n = 280).	Clinical findings, laboratory criteria (serology).	Not suitable “true negative group” used. No information provided on culture and RBT results for this group.
Andriopoulos et al. [33]	RBT, STA, culture	No, DSe and DSp were not assessed because no suitable patient groups were used.	(1) Patients with a history of diagnosis and treatment for brucellosis (n = 83), and 72/83 of these patients were considered chronic/relapsing cases and located and retested 3–13 years after first infection and used for analysis. All cases had acute brucellosis on first infection, but chronic brucellosis cases did not have signs of acute brucellosis illness on presentation the second time.	Based on clinical findings and serology	Not suitable “true positive” patient group because culture was not performed when patients were retested. And DSe was not assessed.	Greece
					No “true negative” patient group used and no DSp assessed.
Mantur et al. [34]	Titrated RBT, SAT, 2-ME, culture.	Yes. DSe and DSp were not assessed correctly.	Patients presented with clinical signs of brucellosis (n = 200). Patients were divided into three groups on the basis of the duration of illness—acute (<8 weeks, n = 179), subacute (>8 weeks but <52 weeks, n = 9), and chronic (>52 weeks, n = 12).	Clinical features, epidemiological evidence, and serology and culture considered for presumptive clinical diagnosis of brucellosis.	Suitable “true positive” patient group used; culture performed in a subset of 56 patients.	India
					No “true negative” patient group used and no DSp assessed
Erdem et al. [35]	RBT, STA, culture.	No. DSe and DSp were not assessed. No suitable patient groups were used.	Patients with a diagnosis of chronic neurobrucellosis (brucellar meningitis or meningoencephalitis).	Clinical features and laboratory findings (serology and culture).	Not suitable “true positive” patient group defined and used.	Turkey
					No “true negative patient group used and no DSp assessed
Marei et al. [36]	RBT, SAT, 2-ME, LFA IgM and IgG, PCR, culture.	Yes, but DSe and DSp incorrectly calculated and DSp based on unsuitable patient group.	Patients presented with clinical suspicion of brucellosis (n = 50).	Brucellosis diagnosis based on clinical findings confirmed by either a positive blood culture or presence of specific serum antibodies (SAT titer ≥ 1/160).	Suitable “true positive” patient group used but culture-positive patients were few (n = 6).	Egypt
					Not suitable “true negative” patient group used. Patients had signs of brucellosis and were not clear if culture was negative.
Ivanov et al. [37]	RBT, SAT, Coombs, ELISA IgM and IgG, culture.	No	Patients with and without clinical signs of brucellosis (n = 63). Patients with brucellosis (n = 21) categorised as acute (duration up to 12 months, n = 6) and chronic (more than 12 months, n = 15), and others were healthy (n = 42).	Clinical picture and serology.	Not suitable “true positive” patient group used. Culture not performed.	Bulgaria
					No “true negative” patient group used. Culture not performed on “healthy” group and no DSp assessed.
Araj et al. [27]	ELISA (IgG, IgM, IgA), RBT, culture, MAT, SA.	Yes	Patients with brucellosis (n = 380), categorised into acute brucellosis (duration < 2 months, n = 296), subacute brucellosis (duration of 2 months to 1 year, n = 44), and chronic (duration > 1 year, n = 40). Other patient groups used included patients with central nervous system brucellosis: patients with CNS brucellosis (n = 45) and patients without CNS brucellosis (n = 66); patients with meningitis not caused by Brucella (n = 62) and patients without meningitis (n = 144).	Clinical picture, laboratory findings (serology, culture).	Suitable “true positive” patient group used. Based on culture-positive results and clinical findings.	Kuwait
			Patients used as “controls” (n = 345) included: patients with other infectious diseases (n = 118), patients with noninfectious diseases (n = 20), and normal healthy individuals (n = 207).	Clinical picture, laboratory findings (serology, culture).	Suitable “true negative” patient group used. Based on culture and clinical findings.

DSe: diagnostic sensitivity, DSp: diagnostic specificity, SAT: serum agglutination test, STAT: standard tube agglutination test, STA: Wright standard tube agglutination, Coombs: antihuman globulin test, FPA: fluorescent polarization assay, LFA: lateral flow assay, LFiC: lateral flow immunochromatography assay, MAT: microagglutination test, Brucellacapt: immunocapture-agglutination test, 2-ME: 2-mercaptoethanol test, CFT: compliment fixation test, SA: Brucella melitensis-stained antigens. Titrated RBT: serum dilutions made in phosphate-buffered saline and then tested with an equal volume of RBT reagent. “True positive” and “true negative groups: “true positive” patient group is defined as patients considered to have brucellosis based on culture-positive results and/or clinical and/or epidemiological criteria. “True negative” patient group is defined as patients considered to be brucellosis-free based on either culture-negative result or clinical and/or epidemiological data. NA: additional patient comparison group used to assess DSe and DSp but not considering “true positive” or “true negative patient groups.