^{1}

^{2}

^{1}Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA

^{2}Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, 17177 Stockholm, Sweden

Academic Editor: Armando Gonzalez

Methods are needed for determining program endpoints or postprogram surveillance for any elimination program. Cysticercosis has the necessary effective strategies and diagnostic tools for establishing an elimination program; however, tools to verify program endpoints have not been determined. Using a statistical approach, the present study proposed that taeniasis and porcine cysticercosis antibody assays could be used to determine with a high statistical confidence whether an area is free of disease. Confidence would be improved by using secondary tests such as the taeniasis coproantigen assay and necropsy of the sentinel pigs.

Neglected tropical diseases (NTDs) are the most common infections of the world's poorest people and the leading causes of chronic disability and poverty in low- and middle-income countries [

Molyneux et al. [

Cysticercosis, caused by

Methods that detect stage-specific antibodies for cysticercosis and taeniasis are available and perform well, yet it is important to know if these serological diagnostic tests are sufficient methods for verifying the elimination of cysticercosis. The available serological test for taeniasis detects antibodies against the

Filariasis control programs [

The sensitivity of a test is defined as the ability of the test to correctly identify those with disease and specificity defined as the ability to correctly identify those with no disease. Both are determined by well-defined specimens, truly positive (disease-positive based on the reference or gold standard diagnosis) and truly negative specimens. For taeniasis, the reference standard for diagnosis is identification of

Based on evaluations using sera that meet these reference standard definitions of true positives and negatives [

Based on the ideas from lymphatic filariasis and onchocerciasis control efforts [

We used the following notations:

Theoretically, the number of positive tests

Note that what we guarantee (with confidence > 100c%) is that the prevalence < target limit

Based on a target of 1% prevalence and the test performance characteristics for the porcine antibody detection test, the LLGP EITB, and the taeniasis antibody test, we determined the maximum number of positive tests allowed for a fixed sample size (

To assess what sample size is needed in a survey, we can assess the probability of declaring that a region is free of disease given a survey with sample size

Is it better to have a test that is highly sensitive but less specific, or highly specific but less sensitive? We compared the probability of a region declared clean or disease-free at sample sizes of 1000 and 2500, under two different combinations of sensitivity-specificity (

Although Weill and Ramzy [

To increase its practical value, it is worth extending our procedure in at least two directions: (i) allow for a cluster sampling procedure and (ii) account for a finite-sample correction. The first extension overcomes the limitations of the simple random sampling design used in our calculations.

If necessary to decrease the sample size, a group of sequential testing methods could be used; with this method, if the data show that the probability of being disease-free is either highly probable or highly improbable, then the data collection can be stopped earlier than planned. An advantage in eliminating cysticercosis is that high-performance coproantigen test is also available. Only active, current infections will produce positive results with the coproantigen test. Combining rapid diagnostic tests for taeniasis and coproantigen tests for the positive subjects will give a powerful indicator of the potential absence of transmission of disease.

With these effective strategies, antibody detection for taeniasis in human subjects and antibody detection for porcine cysticercosis, defining endpoints for control is possible. To reduce the number of samples needed to make determinations for control, additional testing using the coproantigen test in antibody positive taeniasis individuals can be performed.

The authors appreciate the help of Rachel Wolf for editing the paper.

Taeniasis-cysticercosis life cycle and means of verification.

Different sensitivity and specificity scenarios. Each panel shows the probability of declaring a region is free of disease (clean) as a function of true prevalence. It is computed based on 99% confidence at prevalence target 2%. Higher probability at zero prevalence is more desirable.

Upper limit (

Sample size | 100 | 500 | 2500 | 5000 | 7500 |
---|---|---|---|---|---|

Taeniasis (specificity 96%) | 1 | 15 | 99 | 211 | 325 |

Cysticercosis (specificity 98%) | 0 | 8 | 55 | 120 | 187 |

Probability of declaring a region is disease-free given that the region has true zero prevalence; a high value of the probability is desirable. Sensitivity is assumed equal to 94%.

Sample size | 100 | 500 | 2500 | 5000 | 7500 |
---|---|---|---|---|---|

Taeniasis (specificity 96%) | 8.7% | 15.1% | 48.6% | 79.8% | 93.2% |

Cysticercosis (specificity 98%) | 13.3% | 33.1% | 78.7% | 97.8% | 99.9% |