AgentSkillsCN

bio-flow-cytometry-differential-analysis

对细胞术数据进行差异丰度与状态分析。利用统计方法比较不同条件下的细胞群。适用于在测试各组间细胞频率或标记物表达是否存在显著变化时使用。

SKILL.md
--- frontmatter
name: bio-flow-cytometry-differential-analysis
description: Differential abundance and state analysis for cytometry data. Compare cell populations between conditions using statistical methods. Use when testing for significant changes in cell frequencies or marker expression between groups.
tool_type: r
primary_tool: CATALYST

Differential Analysis

Differential Abundance (DA)

r
library(CATALYST)
library(diffcyt)

# Load clustered data
sce <- readRDS('sce_clustered.rds')

# Create design matrix
design <- createDesignMatrix(ei(sce), cols_design = 'condition')

# Create contrast
contrast <- createContrast(c(0, 1))  # Treatment vs Control

# Differential abundance test
res_DA <- testDA_edgeR(sce, design, contrast, cluster_id = 'meta20')

# View results
rowData(res_DA)$cluster_id
rowData(res_DA)$p_adj

# Significant clusters
sig_DA <- rowData(res_DA)$p_adj < 0.05
table(sig_DA)

Differential State (DS)

r
# Test for marker expression differences within clusters
res_DS <- testDS_limma(sce, design, contrast,
                        cluster_id = 'meta20',
                        markers_include = rownames(sce)[rowData(sce)$marker_class == 'state'])

# Results per marker per cluster
ds_results <- rowData(res_DS)

Visualization

r
# DA results heatmap
plotDiffHeatmap(sce, res_DA, all = TRUE, fdr = 0.05)

# DS results heatmap
plotDiffHeatmap(sce, res_DS, all = TRUE, fdr = 0.05)

# Abundance by condition
plotAbundances(sce, k = 'meta20', by = 'cluster_id', group_by = 'condition')

Manual Statistical Testing

r
library(tidyverse)

# Get cluster frequencies per sample
freqs <- colData(sce) %>%
    as.data.frame() %>%
    group_by(sample_id, condition, cluster_id = cluster_ids(sce, 'meta20')) %>%
    summarise(n = n(), .groups = 'drop') %>%
    group_by(sample_id) %>%
    mutate(freq = n / sum(n) * 100)

# Test each cluster
test_abundance <- function(df, cluster) {
    cluster_data <- filter(df, cluster_id == cluster)
    ctrl <- filter(cluster_data, condition == 'Control')$freq
    treat <- filter(cluster_data, condition == 'Treatment')$freq

    if (length(ctrl) >= 2 && length(treat) >= 2) {
        test <- t.test(treat, ctrl)
        return(data.frame(
            cluster = cluster,
            fc = mean(treat) / mean(ctrl),
            pvalue = test$p.value
        ))
    }
    return(NULL)
}

results <- map_dfr(unique(freqs$cluster_id), ~test_abundance(freqs, .x))
results$padj <- p.adjust(results$pvalue, method = 'BH')

Mixed Effects Models

r
library(lme4)
library(lmerTest)

# For paired/repeated measures designs
# Random effect for patient/donor

fit_mixed <- function(df, cluster) {
    cluster_data <- filter(df, cluster_id == cluster)

    model <- lmer(freq ~ condition + (1|patient_id), data = cluster_data)

    coef <- summary(model)$coefficients
    return(data.frame(
        cluster = cluster,
        estimate = coef[2, 'Estimate'],
        pvalue = coef[2, 'Pr(>|t|)']
    ))
}

CITRUS (Automated Discovery)

r
library(citrus)

# Prepare data
fcs_files <- list.files('data', pattern = '\\.fcs$', full.names = TRUE)
labels <- c(rep('Control', 2), rep('Treatment', 2))

# Run CITRUS
citrus_result <- citrus(
    fcs_files,
    labels,
    fileSampleSize = 1000,
    featureType = 'abundances',
    modelType = 'glmnet',
    family = 'classification'
)

# Get significant clusters
citrus_plot(citrus_result)

Volcano Plot

r
library(ggplot2)

# From DA results
da_df <- as.data.frame(rowData(res_DA))
da_df$significant <- da_df$p_adj < 0.05

ggplot(da_df, aes(x = logFC, y = -log10(p_adj), color = significant)) +
    geom_point() +
    geom_hline(yintercept = -log10(0.05), linetype = 'dashed') +
    geom_vline(xintercept = c(-1, 1), linetype = 'dashed') +
    scale_color_manual(values = c('gray', 'red')) +
    theme_bw() +
    labs(title = 'Differential Abundance')

Export Results

r
# Combine DA and DS results
da_results <- as.data.frame(rowData(res_DA))
da_results$analysis <- 'DA'

ds_results <- as.data.frame(rowData(res_DS))
ds_results$analysis <- 'DS'

# Save
write.csv(da_results, 'da_results.csv', row.names = FALSE)
write.csv(ds_results, 'ds_results.csv', row.names = FALSE)

Multiple Comparisons

r
# For multiple conditions
design_full <- model.matrix(~ 0 + condition, data = ei(sce))
colnames(design_full) <- levels(factor(ei(sce)$condition))

# Multiple contrasts
contrasts <- makeContrasts(
    TreatA_vs_Ctrl = TreatmentA - Control,
    TreatB_vs_Ctrl = TreatmentB - Control,
    TreatA_vs_B = TreatmentA - TreatmentB,
    levels = design_full
)

# Test each contrast
res_list <- lapply(1:ncol(contrasts), function(i) {
    testDA_edgeR(sce, design_full, contrasts[, i], cluster_id = 'meta20')
})

Related Skills

  • clustering-phenotyping - Cluster data first
  • gating-analysis - Compare gated populations
  • differential-expression/de-results - Similar statistical concepts