Grouping variables in a Column

General
2

You can do something like this

library(tidyverse)

# Sample data on a copy/paste friendly format, replace with your actual data frame.
sample_df <- data.frame(
    stringsAsFactors = FALSE,
    Final.Test.Result = c(NA,"Discordant",
                          "HIV-1 Negative","HIV-1 Positive","HIV Negative",
                          "HIV Positive, undifferentiated","Inconclusive, further testing needed",
                          "Invalid","Negative","Positive","Preliminary positive"),
    Count = c(328L,5L,88L,72L,5304L,1L,
           30L,10L,37722L,110L,17L)
)

sample_df %>% 
    mutate(group = case_when(
        str_detect(Final.Test.Result, "[Pp]ositive") ~ "Positive",
        str_detect(Final.Test.Result, "[Nn]egative") ~ "Negative",
        TRUE ~ "Other"
    )) %>% 
    group_by(group) %>% 
    summarise(Count = sum(Count))
#> # A tibble: 3 x 2
#>   group    Count
#>   <chr>    <int>
#> 1 Negative 43114
#> 2 Other      373
#> 3 Positive   200

Created on 2021-03-26 by the reprex package (v1.0.0.9002)

Note: Next time please provide a proper REPRoducible EXample (reprex) illustrating your issue.