Ethical approval for the data collection was granted by the University College London Research Ethics Committee (reference: 8075/001) and Malawi National Health Sciences Research Committee (reference: 16/4/1568). The child’s caregiver (including parents, grandparents or older siblings) who was present with them at the hospital provided informed verbal consent for the clinical assessments, anthropometric and BIVA measurements. The verbal consent process was approved by the research ethics committees and was explicitly recorded within the study’s electronic data collection tool; verbal information and consent was used due to literacy levels of caregivers. FGD participants provided informed written consent. The information given to all participants before consenting included the process for data anonymization prior to sharing.

The study was conducted at Mchinji District Hospital, in the central region of Malawi. The hospital provides a secondary level of care, with paediatric and neonatal inpatient wards but limited intensive care capacity. It acts as the main referral facility for the district, which has a population of approximately 600,000, and is mostly rural with a subsistence farming economy. The 2016 Demographic Health Survey reported 10.7% of children under five years were underweight and 32.6% were stunted in Malawi ¹⁸ .

Sampling . Children were recruited using a purposive convenience sampling approach, with the aim to have variation in age, nutritional and HIV status, and equal numbers of those with pneumonia and without pneumonia or another acute infection. We did not conduct a sample size calculation given the exploratory design, but set a pragmatic target of recruiting 50 children with and without pneumonia. Inclusion criteria were being 0–59 months of age and having no previous participation in the study. Children were recruited from the paediatric inpatient ward and outpatient clinic at the hospital (which includes growth monitoring and routine vaccinations). Healthcare workers alerted study staff when children with suspected pneumonia presented and study staff reviewed ward admission notes daily. All children were then screened by study staff for pneumonia using WHO’s Integrated Management of Childhood Illnesses (IMCI) guidelines, enhanced with pulse oximetry ⁹ . Healthy children were defined as those who did not have any signs of pneumonia or another acute illness, and were not admitted to the paediatric ward (e.g. children presenting for routine vaccination).

Data collection . Socio-demographic, clinical, anthropometric, and BIVA data were collected by two clinical study staff (BZ and EK), supported by a clinical officer working in the paediatric ward. Staff underwent one-week of training, including: BIVA measurements, refresher anthropometry training, supervised field testing and piloting. All children underwent a clinical pneumonia examination, followed by the anthropometric and BIVA measurements. Other clinical data was extracted from the child’s routine medical records (e.g. malaria and HIV status). Each of the following anthropometric measurements were taken twice, in immediate succession: weight, length (for children <2 years) or height (for children aged 2–5 years) and mid-upper arm circumference (MUAC). Weight was measured using a Salter scale or standing scale, depending on the child’s ability to stand unaided.

BIVA measurements were taken using the BodyStat 1500MDD battery operated machine. The child was positioned on their back, and sensor pads were placed at the testing locations, with 3cm between electrodes. The following BIVA measurements were taken twice in immediate succession: full body, trunk, and arm ( Figure 1). To reduce the movement of children during the measurement, children who were not able to lie calmly were held in place using either a “hugger” (a paediatric immobilizer commonly used for x-rays and scans), or the caregiver held them in position with a folded cotton cloth used as a barrier to the electric current. This pragmatic testing protocol was developed during a piloting period conducted before recruitment for this study, where the influence of movement, position and restraint on measurement results was explored. The following outputs for BIVA were recorded for each measurement site: phase angle at 50kHz, resistance at 50kHz and reactance at 50kHz. The phase angle is calculated as (reactance/resistance)×(180°/π); it represents cell mass and cellular health, with higher values hypothesized to reflect higher lean mass and better cell function, hydration, and higher cell membrane integrity ^{11, 14, 19} .

Analysis . Reliability of BIVA and anthropometric measurements was calculated as the difference between the first and second measurements. All differences between the first and second measurements were converted into positive numbers, and the mean, standard deviation and 95% confidence intervals of the mean for each measure calculated. To investigate the relationship between MUAC and WAZ (exposures), and phase angle for the full body, trunk, and arm segments (outcomes) we conducted linear regression adjusted for age and sex ^{20, 21} , and stratified by pneumonia status. Children with missing data for any variable were excluded from analyses, as a complete case analysis. Analysis was done using Stata 15.1.

Sampling . The healthcare workers were purposively sampled for the FGDs, with two FGDs planned. The first included community healthcare workers, locally know as Health Surveillance Assistants (HSAs), who had not participated in any other recently on-going pneumonia studies in the district ²² . The second FGD included healthcare workers working at Mchinji District Hospital, but who had not previously participated in the BIVA study. Participants were invited to take part by phone, following approval to leave their posts from the District Health Officer.

Data collection . The FGDs were facilitated by a local female nurse (EK, ENM qualification) experienced in qualitative research. FGDs were also attended by the project coordinator, a male clinical officer (BZ, Diploma qualification), to introduce the project and answer specific questions relating to the BIVA technology. Both EK and BZ had worked on community and facility-based research in Mchinji District and were present in the hospital for the quantitative data collection, they may therefore have had prior interactions with FGD participants in a research capacity. Prior to the discussions, the participants were given a demonstration on how to use the BIVA machine, an explanation of its function and purpose, and the overall purpose of the study.

The discussion followed a structured guide, with the following topics: current malnutrition assessment methods, burden of malnutrition, initial impressions of the device, improvability, and proposed modifications (see Extended data ²³ ). The FGDs were conducted in a mixture of English and Chichewa, based on participant preference and lasted between 25–45 minutes. Discussions were audio recorded following participant consent and then transcribed and translated as a team by BZ and EK (see Underlying data. Field notes were not used, and the transcripts were not returned to participants for checking.

Analysis . The data was analysed thematically using framework analysis by HD ²⁴ . Framework analysis was selected due to its systematic matrix approach to allow comparison between participants’ viewpoints. After reading through the transcripts multiple times for familiarization, the transcripts were single coded by HD in their entirety using the freely available OpenCode 4.03 software with supervision from CK. The descriptive codes were summarized into categories, and then into inductive themes relevant for addressing the research aim. The transcripts were then re-read to verify that the analytic framework was still reflective of the transcripts. Transcripts were then indexed, and quotes from the FGD participants were charted into the framework. To cross-validate and triangulate the findings, the final interpretation was discussed and agreed between HD, BZ and CK; we did not seek feedback on our interpretations from participants.

Overall, we recruited 52 children ( Table 1) ²⁵ . Although the children with and without pneumonia were comparable by sex distribution, the children with pneumonia were younger than the healthy children (mean age in months: 13.53 vs. 28.57, p-value <0.001). The mean phase angle of the children with pneumonia was lower in all three BIVA measurements compared to the children without pneumonia.

Table 2 describes the reliability of measurements. Overall, the variation was larger for the children with pneumonia than healthy children for all measures, except weight. For the BIVA measures, the mean difference in the phase angle was similar across the three sites, with a mean difference of 0.20 (95% CI: 0.06, 0.34) for full body, 0.25 (95% CI: 0.17, 0.34) for the trunk and 0.29 (95% CI: 0.18, 0.39) for the arm. Resistance values varied considerably between measurements.

Table 3 shows the adjusted association between WAZ and MUAC with the BIVA phase angle, for each of the three BIVA measurements. The direction of associations between WAZ and MUAC exposures and phase angle were negative for all measures in pneumonia cases, with the strongest associations for trunk measurements (WAZ: aCoeff: -0.261; 95%CI: -0.523, 0.001; MUAC: aCoeff: -0.044; 95%CI: -0.065, -0.024). With the exception of the arm measurement, the direction of association was positive for healthy children, but none were statistically significant.

A total of 11 healthcare workers participated in the two FGDs (five in the hospital discussion and 8 in the community healthcare worker discussion), with all those invited taking part. Through the framework four inductive themes emerged, which are summarized in Box 1: trust in technology, capacity, sustainability, and device usability.

Trust in technology . This theme encompasses the healthcare workers trust and mistrust of the BIVA technology, as well as how they perceived caregivers would accept and trust that appropriate care was being provided.

Based on the demonstration of the BIVA machine, many participants expressed that BIVA would provide an accurate and time saving method to assess the nutritional status of children. There was also trust that with BIVA, malnourished children who are not identified by the current measurements, would be identified given the perception of the device being inherently more accurate.

However, this view was not universal, and some participants expressed hesitation around BIVA due to the lack of knowledge on potential side effects or functionality. They indicated the need for monitoring and evaluation of the technology to be sure it is trustworthy and safe. Similar to their own concerns, the healthcare workers raised the issue of caregivers being worried the device could cause harm, discussing that if a negative perception or myth around BIVA arose it would then be hard to gain their trust. However, other participants said that it would not only be accepted, but it would increase trust in the health system.

The communication and terminology used with caregivers was discussed as a key determining factor of whether they would accept BIVA.

Capacity . Capacity emerged in the context of both a barrier and opportunity of BIVA, with the following sub-themes: capacity building through training, increasing capacity through adequate resourcing and self-determination.

Participants in both FGDs voiced the need for education and training on how to use BIVA before they would feel confident. Specifically, the issue of where and how to place the electrodes on the child was addressed by many participants as a something they would need training on. They also voiced the need for community education on BIVA prior to implementation to increase the knowledge of caregivers.

A reported barrier to current malnutrition assessments was a lack of capacity due to limited resources. This opinion was shared by all participants in the FGD with hospital-based healthcare workers, but wasn’t reflected by the HSAs. Many resources were mentioned as being insufficient – time, tools such as a height board or scale, and knowledge. Some participants stated that BIVA has the potential to solve those problems and increase their capacity to assess malnutrition since currently nutritional status is only being measured by one department in the hospital. However, this was based on the participants’ assumption that BIVA would be made available in multiple departments.

Related to this was a lack of self-determination, with healthcare workers in the hospital FGD expressing concern that due to the overwhelming workload and lack of resources, other healthcare workers don’t make efforts to properly identify and treat malnutrition.

Sustainability . The theme of sustainability includes the sustained practice of implementing BIVA as an indicator of malnutrition, and the physical sustainability of the tool itself. For sustained practice, concerns were raised over how many BIVA machines would be available and who would use them. One participant explained that for BIVA to be successful there would need to be a broad distribution of machines in different wards of the hospital.

The overall concern voiced by almost every participant was that necessary resourcing would need to be secured, otherwise the implementation of BIVA would be unsustainable.

The sustainability of the device was reflected by participants raising questions regarding maintenance and fragility. Most participants also pointed out that the BIVA machine needs constant supplies such as batteries and stickers for the electrodes and running out of either would mean the end of implementation. Despite these barriers, participants overall remained positive that if sufficient resources are available, successful implementation would be possible.

Device usability . The theme of usability includes healthcare workers’ initial reaction to the demonstration, and their ideas to improve the device to make it more user friendly. Almost all participants were positive that the BIVA tool would decrease their workload and be simple to use. For some it wasn’t intuitive, but they felt more confident that it would be a useful tool after seeing the demonstration.

Many participants in both FGDs stated that the BIVA tool would be more user friendly than determining malnutrition using z-scores as obtaining the date of birth and interpreting age-specific results is a key implementation barrier.

Several ideas of how the device could be improved were proposed, the main one being to make the device solar powered instead of using batteries. Participants also expressed a preference for re-usable alternative to the sensor stickers, instead of needing to replace the disposable ones. The facilitators had introduced in their demonstration that the manufacturers were considering alternative ways of attaching electrodes, such as bracelets or cuffs, and many participants were supportive.

One participant proposed that the BIVA machine could be improved with the addition of audio outputs. Another proposed that the measurements would be simplified if children could remain dressed for measurements, which was put forward as time-saving and would make the procedure more acceptable to caregivers of sick children.

Figshare: BIVA Malawi Project. https://doi.org/10.6084/m9.figshare.c.6052871 ²⁵ .

This project contains the following underlying data:

Figshare: Bioelectrical impedance vector analysis in Malawi – Supplementary Appendix 1 (FGD topic guide). https://doi.org/10.6084/m9.figshare.19801756 ²³ .

This project contains the following extended data:

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).