Table 2.

Frequency of the individual HLH-2004 classification criteria according to the data included in studies centred on collect HLH-related features in COVID-19 patients [34–43]

HLH features	N	n	%	First author (reference)
Hepatomegaly and/or splenomegaly	152	23	15.1	Hakim [34], Loscocco [35], Prieto-Pérez [36], Ruscitti [37], Wood [33]
Cytopenias (2 lineages)	990	32	3.2	Feld [38], Hakim [34], Loscocco [35], Prieto-Pérez [36], Ruscitti [37], Wood [33]
Cytopenias (3 lineages)	152	6	3.9	Hakim [34], Loscocco [35], Prieto-Pérez [36], Ruscitti [37], Wood [33]
Ferritine > 500 ng/mL	895	738	82.4	Feld [38], Hakim [34], Prieto-Pérez [36], Wood [33]
Ferritine > 1000 ng/mL	855	513	60	Feld [38], Hakim [34], Prieto-Pérez [36]
Ferritine > 10,000 ng/mL	895	57	6.3	Feld [38], Hakim [34], Prieto-Pérez [36], Wood [33]
Ferritine < 2000 ng/mL	135	90	66.6	Loscocco [35], Ruscitti [37], Wood [33]
Ferritine 2000–6000 ng/mL	135	33	24.4	Loscocco [35], Ruscitti [37], Wood [33]
Ferritine > 6000 ng/mL	135	12	8.8	Loscocco [35], Ruscitti [37], Wood [33]
Hypertriglyceridaemia	975	90	9.2	Feld [38], Hakim [34], Loscocco [35], Ruscitti [37], Wood [33]
Hypofibrinogenaemia	1003	14	1.3	Feld [38], Hakim [33], Lee [39], Loscocco [35], Ruscitti [37], Wood [33]
Haemophagocytosis	60	19	31.6	Prieto-Pérez [36], Wood [33]
HLH > = 5 criteria	22	0	0	Feld [38]
HScore > 169	428	17	3.9	Clark [41], Giamarellos-Bourboulis [42], Hakim [3], Ruscitti [37], Wood [33]