## 2 Materials and Methods  
### Study Design and Data Collection  
The microbiology laboratory in study is located in a tertiary hospital in the north of Spain.  
Focus group interviews (FGIs) with the laboratory healthcare professionals were carried out to collect data in the study. FGIs were used to explore the serology clinicians' and technicians' views and opinions regarding the current serology processes, to gather relevant clinical information and to validate proposals along the different phases of the study. Two focus groups were defined: one with microbiology specialists and one with the serology technicians. As the minimum number of members required for a focus group is between three and five participants [56], the head of the microbiology section, two clinicians and four technicians were recruited. The focus group interviews, conducted throughout various stages of the study (pre-TLA and post-TLA), were limited to a maximum duration of one hour each.  
The study was longitudinal, extending the period in study from January 2020 to May 2022, before and after the implementation of Lean methodologies and Total Laboratory Automation (TLA) in the facilities. Data were extracted from the laboratory information system (LIS), considering a period of eight months after deployment of the TLA in September 2021, to ensure the stability of the process and the information collected after the ramp-up period. From June 2020 to March 2021, the laboratory handled 233,266 serology tests, accounting for an increase of 85% versus the same observation period the previous year. This was due to the boost in COVID-19 serology test requests, which represented 58% of the total serology tests processed in the laboratory in that period. Among the non-COVID-19 serology tests, HIV accounted for 19%, being one of the most frequent tests, together with Hepatitis B surface antigen--HBsAg(18.4%), hepatitis C--HCV (15.6%) and syphilis (11.6%).  
Concerning the laboratory output, the laboratory handled 210,315 serology tests in 2022. During the period of study, 77,216, 40,999 and 18,273 COVID-19 serology samples were processed in 2020, 2021 and 2022, respectively. For HIV tests, the volume of samples processed was 26,447, 27,997 and 29,216 for the mentioned years.  
In COVID-19 serology tests, two SARS-CoV-2 antigens, the nucleocapsid (N) and spike (S) protein, are identified with antibody detection assays using different techniques such as chemiluminescence immunoassay (CLIA). Different antibodies are also measured in the tests, immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin A (IgA) or total immunoglobulin [57].  
Based on the data extracted from the LIS and the clinicians' feedback in the focus group interview held at the beginning of the study for the selection of the key serology test types to analyse, two process workflows were defined: (i) HIV serological samples, (ii) total nucleocapsid (COVT) and spike IgG (COVIDGG) SARS-CoV-2 antibody testing.  
The peak period of samples arrival in the laboratory was between 09:30 AM and 11:30 AM, decreasing the load in the early evening. Process observation and data collection were performed during the complete working shift--from 8:00 AM to 3:00 PM.