Programme implementation is vital in achieving and strengthening desired health intervention results. Effective implementation of an intervention at a health facility requires combined multi-sectoral effort, i.e. it relies on both the facility managers, the health care providers or workers and facility resources for the intervention to improve health outcomes. A review of several health care interventions implemented within health facilities revealed that the programmers had provided guidelines for management and core implementers (health workers) to aid implementation [1, 2]. For example, the policy guideline for conducting TB screening among PLHIV attending HIV clinics in Ghana contained specific guidelines and activities to be provided by the facility as a unit and another set of policies and activities to be delivered by the health worker for the intervention to be successfully implemented in the facility . However, there exists little information on the extent of holistic implementation of the intervention.
Most studies assessed fidelity of delivery separately, either at the facility level or the provider level. However, there might be variations in facility resources which might skew the comparison. Though the provider level or facility level adherence or fidelity provides an important measure for identifying specific components for implementation improvement and tracking the progress, they fail to provide an easily accessible picture of the performance of the implementation  on an intervention outcome. According to the Institute of Medicine (IOM) , combined measures are an aggregation of individual performance measures into a summary score, thereby reducing the amount of data to be processed, leading to a clearer picture of overall fidelity. It serves multiple purposes, including the "provision of a summary of the extent to which management has created a "culture of excellence" and designed processes to ensure high performance in delivering services throughout the organization, benchmarking of organization's performance against high-performing organizations and to monitor changes over time, tracking a particular components' performance, providing performance criteria to use in selecting high-performing facility, and for identifying high-performing facilities which can then be studied to identify characteristics that distinguish them from lower-performing facilities" .
Implementation science research assessments of health interventions revealed that interventions are mostly not delivered as designed by the intervention's designers. This is referred to as implementation fidelity or adherence to the delivery [6–8]. As discussed earlier, some of these studies assessed fidelity of delivery from either the health workers' perspective  or the facility (managers') perspective . Weighted fidelity to combine both are lacking in the implementation science literature. The term weighted fidelity is used in this study as an umbrella to refer to the combination of whether the facility managers adhere to protocol guidelines of the implementing the TB screening intervention at the facility and whether the HIV healthcare provider adheres to the clinical guidelines and activities for delivering the intervention as is. Weighted fidelity, a composite measure, is essential to fully understand the extent of implementation to maximize the potential for effectiveness and relate to observed intervention outcomes.
Implementation fidelity (including 'weighted' fidelity) is a component of process evaluations [11, 12], which documents whether the intervention activities have been delivered as intended and resulted in a separate output [12, 13]. Process evaluation may be conducted periodically at any phase of the intervention evaluation  by reviewing the activities and output components to assist stakeholders in seeing how the intervention is performing. That is, the assessment can be done at the feasibility, effectiveness or implementation stages. Weighted fidelity of delivery is a complex mix of health providers' and facility managers' adherence. The TB screening activities from the providers' level will have to be aggregated at the facility level and combined with the facility managers' TB screening implementation activities. Studies have proposed and used different evaluation methods to fully understand the extent of the implementation . Mixed methods evaluations had been proposed by some studies [15, 16]. Other studies also proposed quantitative methods through observation and self-reporting , recording of sessions, transcription, and rating a random proportion against a checklist [8, 17] to assess fidelity of delivery. Irrespective of all these approaches, multiple methods have been recommended to overcome the limitation of the individual methods [18–21]. They proposed that more consideration on the choice of method should be placed on the resources available for conducting the study and the context in which the study is to be undertaken. Quantitative approach through self-reported and record reviews work alternatively well when the research is resource-constrained and if stigmatization was going to be an issue especially when observation was going to be a paramount choice of method. This latter approach also provides in-depth understanding of the factors influencing fidelity  and is able to relate fidelity of delivery to intervention outcomes observed.
Fidelity of delivery occurs within the implementation process  to achieve intervention outcomes. The extent of full delivery of the intervention is also influenced by some factors including availability of resources, health workers, workspace, etc. . To take the complexities of the fidelity assessments and its related factors into account, a theory needs to include factors that potentially influence fidelity and the components for determining fidelity. Many frameworks to assess fidelity exist. One such integrated framework is the Conceptual Framework for Implementation Fidelity by Carroll et al. .
Carroll et al.'s  framework provides guidance to measure fidelity and its related factors. The framework proposed that the relationship between the implementation of evidence-based intervention and its outcome may be influenced by fidelity (the extent to which the intervention is delivered as is). They proposed further that "the measurement of implementation fidelity is the measurement of adherence, i.e., how far those responsible for delivering an intervention actually adhere to the intervention as its designers outline it. Adherence includes the sub-categories of content, frequency, duration and coverage (i.e., dose). The degree to which an intervention's intended content or frequency is implemented is the degree of implementation fidelity achieved for that intervention. The level achieved may be influenced or affected, (i.e., moderated) by certain other variables: intervention complexity, facilitation strategies, quality of delivery, and participant responsiveness" Finally, according to Carroll et al. , when the critical components of an intervention are identified and implemented well, then an implementation said to be successful. The framework provides a systematic method that can be used to assess fidelity and its related factors and has previously been used in different sectors of life [23, 24]. However, to the best of the authors' knowledge, no research had ever assessed weighted fidelity of delivery. Therefore, this study extends previous research by using a systematic approach to advance initial strategies that could be used to improve fidelity assessment in the health sector.
The strategies outlined in this paper are to be well-thought-out within the context of TB screening among PLHIV attending HIV clinics in Ghana. TB screening is an early TB detection strategy aimed at decreasing the burden of TB in PLHIV and AIDS. The technical policy and guidelines for TB/HIV collaboration in Ghana spelt out various activities and guidance to pursue at multiple facilities. The TB screening intervention was to be carried out "as part of the health sector response to the intersecting TB and HIV epidemics (sector-wide approach –SWAP), and as part of the essential health care package (EHP) in Ghana" . The intervention consisted of standard components delivered by the facility managers and components provided to all HIV clients by the HIV health worker. Details of the intervention components for the managers are reported in the facility level fidelity paper , while that of the HIV care providers are reported in the provider level fidelity paper .
Utilizing the Conceptual Framework for Implementation Fidelity, this study aimed to demonstrate one way in which fidelity can universally be assessed to improve intervention outcomes. The paper specifically aimed to:
Assess weighted fidelity of delivery to the intervention
Identify factors influencing weighted fidelity of delivery, and
Relate the weighted fidelity scores with the respective TB screening coverage.