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Perforin and CD107a testing are superior to NK cell function testing for screening patients for genetic HLH

Tamar S. Rubin, Kejian Zhang, Carrie Gifford, Adam Lane, Jack J. Bleesing and Rebecca A. Marsh

Key points

  • Compared to perforin and CD107a expression, the NK cell function test is less sensitive and no more specific for discriminating genetic HLH.

  • Perforin and CD107a testing could augment NK cell cytotoxicity testing for use in HLH diagnostic criteria.

Abstract

Primary HLH (hemophagocytic lymphohistiocytosis) can be caused by bi-allelic mutations in PRF1, encoding perforin, or UNC13D, STXBP2, STX11, RAB27A, LYST and AP3B1, encoding proteins involved in cytotoxic lymphocyte degranulation. Natural killer (NK) cell cytotoxicity assays can quickly screen for all these genetic diseases, facilitating treatment, but combining NK cell perforin expression and CD107a upregulation tests can as well. To determine the relative diagnostic accuracies for each approach, we retrospectively reviewed screening test performance in 1614 patients referred for HLH evaluation. For each test, we generated a receiver operating characteristic (ROC) curve, and calculated area under the curve (AUC) and diagnostic parameters at optimal threshold. We generated an AUC for combining perforin and CD107a tests by creating a logistic regression model and applying model-generated coefficients to patient values. Sensitivities of NK cell function, perforin mean channel fluorescence (MCF), and CD107a MCF to detect bi-allelic mutations were 59.5%, 96.6%, and 93.8%, with specificities of 72.0%, 99.5%, and 73%. AUCs for NK cell cytotoxicity, perforin MCF, CD107a MCF, and combined perforin and CD107a MCFs were 0.690, 0.971, 0.860, and 0.838. Perforin and CD107a tests are more sensitive and no less specific compared to NK cytotoxicity testing for screening for genetic HLH and should be considered for addition to current HLH criteria.

  • Submitted December 19, 2016.
  • Accepted February 19, 2017.